Supernatural's series finale came burdened with understandably high expectations, with viewers and cast broadly in agreement that Sam and Dean Winchester's story was ending at the right time. Supernatural season 15 kicked off with promisingly high stakes too, as God finally revealed his true villainy and made one final rally against those pesky Winchester brothers.
Sadly, Supernatural couldn't stick the landing. The final installment aired in November 2020 to a lukewarm reaction, leaning more toward the maligned Game of Thrones than the lauded Breaking Bad on the spectrum of TV finales. Titled "Carry On," the episode picked up in the wake of God's defeat and essentially tied a bow onto the show's legacy. A wonky, crumpled, slightly-too-loose bow...
On the bright side, Supernatural's retirement has proven short-lived. Prequel spinoff potential Supernatural revival further down the line, describing a gritty, 10-episode HBO Max limited series. Whatever form a Supernatural revival may come in, Sam and Dean's return could fix a few of the criticisms aimed at "Carry On."
Dean Winchester's Anti-Climactic Death
Over the course of Sam and Dean Winchester's Supernatural journey, the brothers overcame angels, demons, archangels, primordial spirits from the beginning of time, and even God himself. It's a track record that earns the brothers a justified reputation among both Supernatural's cacophony of evil-doers and the hunting community. Given all the mighty villains Sam and Dean slay, watching the older sibling die after getting pushed onto a random spike by a no-name vampire was hugely disappointing. As the warrior of Supernatural's starring pair, Jensen Ackles' Dean was always more likely to go down fighting than fade away in old age, and "Carry On" is probably trying to remind fans how even the most routine hunt can be fatal, regardless of reputation.
Ultimately, however, seeing Dean die in such lackluster fashion ends his mortal existence on the weakest possible note. A Supernatural revival would inevitably find some way of bringing Dean Winchester back to life, be that temporarily or otherwise, and Ackles would be afforded a second opportunity to make a fitting exit - i.e. something more heroic against a more significant threat.
Sam Winchester's Family Mysteries (& Bad Costume)
Though Supernatural's ending did Dean Winchester a disservice with a middling death, his brother didn't fare much better in the living realm. "Carry On" reveals Sam settled down with a woman and is father to a child named after its late uncle, but the montage leaves crucial information to the imagination. Sam's better half is a blurry-faced background character - probably Eileen (they're still together in the Supernatural finale's present timeline) but still unidentified. Sam's son does at least appear - played by Spencer Borgeson - but Supernatural then gets frustratingly cagey about his future. A protection tattoo on Dean Jr.'s arm subtly implies he followed in the family business, but considering these tattoos protect against demonic possession, it makes sense that Sam Winchester's son should have one even if he sold insurance in an office.
A Supernatural revival could provide clarity over Sam's relationship status, bringing closure to his relationship with Eileen one way or another, while also indicating whether Dean Jr. continues the Winchester family's lineage of monster killers or breaks the cycle - an important thematic detail that Supernatural's finale skipped. Depending on how far into the future this hypothetical Supernatural revival takes place, Jared Padalecki might also get the opportunity to play an older Sam Winchester without just slipping on a grandpa cardigan and poorly-fitting gray wig...
Supernatural's Missing Finale Cameos
Supernatural's finale missteps were, in fairness, not entirely the show's doing - Supernatural season 15 was unfortunate enough to be filming its final run of episodes in March 2020. When production cautiously resumed after a COVID-19 delay, necessary restrictions were still very much in force, and likely impacted Supernatural's capacity to bring in the returning faces and guest stars that would've helped Sam and Dean depart with the appropriate fanfare. Only Jim Beaver's Bobby Singer made the trip back home, and the absences of Castiel, the Wayward Sisters, Mary Winchester, and numerous other fallen friends that might've greeted Dean in the afterlife are keenly felt.
Now that COVID-19 measures have more or less been dropped, a Supernatural revival could deliver the emotional cast and character reunions "Carry On" sorely lacked, and with Dean straddling the boundary between Heaven and Earth, there's virtually no restriction on which faces might appear. Supernatural could finally do what it probably wanted to do back in 2020.
Chuck's Surprisingly Easy Defeat
After previous seasons featured such storied antagonists as Lucifer, Michael and Amara, God represented the only logical choice for Supernatural's big boss. Nevertheless, the long-awaited showdown didn't match its big-name billing, and though the fight technically happens in Supernatural's penultimate effort, the impact lingers into "Carry On." God's downfall is sealed after a brief exchange of fists against Sam and Dean, followed by the hastily-foreshadowed revelation that Jack is now a power vacuum capable of sucking God's power right out, thus rendering him mortal. This solution would've made for a damp last battle in a regular season finale, let alone a final-ever episode, and past battles against the likes of Azazel, Lucifer and Lilith prove Supernatural is capable of far better.
Again, COVID-19 might need to accept partial blame for the lack of scale and grandeur during Sam and Dean Winchester's last tussle with Chuck. Also again, a Supernatural revival could make reparations. God is left alive as a punishment in Supernatural's second-to-last episode, and while Jack boldly claims the deity's powers shall never return, plenty of Supernatural baddies have overcome greater odds in the name of dragging themselves back to relevancy.
One could, however, argue that if Supernatural did ever revive for a one-off adventure or limited series, Sam and Dean Winchester would be better served returning to their monster-hunting roots, away from obscenely powerful gods and angelic spirits.
Dean & Castiel Romance Confusion
Castiel's Supernatural season 15 death came with a barn-full of controversy. Hunted by Billie, Castiel realized the only way to spare Dean was triggering a deal made previously with the Empty - that his angelic life would be taken during a moment of pure happiness. To summon the primordial creature, Castiel told Dean he loved him, but Supernatural left the true meaning behind those words somewhat vague. Plenty of signs point toward Castiel's confession being romantic in nature - the "moment of happiness" setup, Dean's inability to reply, directing the words toward one Winchester rather than both. Alas, discourse from cast since the scene aired has fallen somewhere between disharmonious and noncommittal, casting ambiguity over exactly which brand of love Castiel spoke of.
Supernatural had an easy solution - reunite Dean and Castiel in the finale. Their reaction would quickly confirm one way or another whether season 15's confession was romantic in nature. That reunion never happened, despite "Carry On" confirming Castiel was helping Jack reorganize Heaven off-screen. If a Supernatural revival were to happen one glorious day, Dean and Castiel would almost certainly cross paths, creating an opportunity to clarify how the angel's emotional last words should be interpreted.