In 2023, Marvel Comics brought back its Ultimate label, but with a twist. It wasn't the Ultimate universe born in the early 2000s that died in Secret Wars. No, it was a different deal. Instead of being a full reboot, this brave new world was born from the machinations of Reed Richards' Maker. The line launched with Ultimate Spider-Man, which explored Peter as a married father of two. Upon its arrival, something unprecedented in comics happened: Everyone loved it. There were basically no complaints about it; there was only unison joy, echoed, at long last, by the grand majority of the comic book community. 
The universe followed up its debut with a slew of new titles—Ultimate X-Men, Ultimate Black Panther and The Ultimates. The titles were like songs in an Olivia Rodrigo album: All bangers. The Ultimate imprint quickly cemented itself as a worthy parallel of the main Marvel Universe. Then, however, a shocker came: Marvel announced the Ultimate world was coming to an end. We still don't know how things will play out for the characters, but there's an idea that hasn't left my brain since reading the announcement... 
Ending the Marvel Universe is a Big Mistake 
Let me preface this by making something clear: This isn't a slight at Marvel. This isn't me saying that the 616 universe has poor storytelling, and that the Ultimate universe somehow saved a shambling House of Ideas. I do not believe that, whatsoever. I love the Marvel Universe, as well as the majority of its adjacent universes. I fell in love with reading Marvel comics with Ultimate Fantastic Four, and my passion for that world hasn't waned. To this day, new 616-set stories almost never fail to fill me with joy.
So, no, this isn't about pitting the 616 and Ultimate lines against one another. Instead, what I'm trying to say is that the Ultimate universe deeply enriched Marvel's legacy. Now, I'm fully aware that the House of Ideas has a plan for ending the Ultimate world. There's a roadmap in place, after all. Yet, despite this clear preparation on Marvel's part, the situation still doesn't feel right. 
Given the fact that it's existed since the '60s and has, for the most part, maintained a single continuity, the Marvel Universe has explored a lot of different stories. As in, a lot. Try reading the Wikipedia page of any major Marvel player, I dare you. You'd get a PhD's worth of education just by going through five of them. My point is, we've seen a lot from our heroes; we know them very well, we know who they're supposed to be. As such, their long histories form expectations around them.
If Wolverine were to suddenly be retconned as having been the Winter Soldier, it would feel strange, because we know ol' Logan. If out of nowhere, the 616 timeline shifted and Aunt May died in place of Uncle Ben, we'd be fairly puzzled. These are firm, canon events for Marvel; they're not supposed to be changed in the main continuity, and thus, they present storytelling roadblocks—roadblocks by design of the universe, granted, but roadblocks nonetheless: How do you explore fresh storylines for these characters without betraying their core structure?
That's where the Ultimate Universe came into play. 
A New Avenue for Stories
The main benefit presented by the new Ultimate universe was, as its core, quite basic: It allowed Marvel to explore stories that couldn't be given to its main characters due to their longstanding legacy. It provided the chance to finally see Peter and Mary Jane in a wonderful and loving marriage; It allowed mutants to be shown in a different light—not within the confines of a cozy school, but out in society, slowly finding each other while still having no idea of who they actually are; the list goes on.
The Ultimate universe is not, and never was, competition for the 616 timeline (not that Marvel ever said it was); it's an added creative outlet; an alternate avenue for the company to try things out that either hadn't been thought of, or were too out there to give to the main versions of its heroes. Best of all, however, not only did the universe allow the company to explore previously unexplored facets of its heroes, the stories were (and continue to be) of the highest quality. That's why letting go of this universe could end up a major creative misstep. 
Look, judging by the quality the Ultimate universe has shown so far, I have no doubt in my mind the ending will be good. I'm expecting it to pack the same gravitas and storytelling prowess that its comics have delivered so far. In fact, there could be a case where the universe comes to a close and we get to see all the pieces perfectly fall into place for it to satisfyingly enrich the main Marvel continuity (since it's been confirmed it will affect the 616 universe). All of that is a real possibility.
Having said that, the disappointing part of all this remains that the universe is ending; that countless story possibilities are being left on the table by doing away with this promising new world. The setup work done by the Ultimate line for so many of its characters is full of untapped potential for unique stories––stories that two years simply aren't enough to fully exploit.
Marvel Comics is an incredible entity. It has provided the world with countless amazing stories, and has introduced us to awe-inspiring characters who push us and encourage us to be better every day. The company's quality standards and the intelligence of those running it are not in question here. Furthermore, this also isn't meant to be a doom call for the company. No, Marvel is not in trouble, and no, losing the Ultimate universe won't cause it to collapse. However, the end of that world is the potential loss of a great opportunity to keep experiminenting with the characters we love, without touching their current continuity. 
Ultimate Spider-Man's last issue will be released in December, 2024.