Superheroes always need to have their big bad villain. While every Marvel movie has its individual antagonists, it's the big, overarching villains that appear in multiple entries (and seem to have a hand in everything) that tend to make the most impact. Marvel has been pretty good so far about setting these characters up well in advance and having them impact the story in ways that make them really feel like a threat. The main example of this is Thanos, who was set up in post-credits scenes early on in the MCU before he made an actual appearance in Avengers: Infinity War, and served as the big bad for the end of the Infinity Saga.
It seems like the MCU might be gearing up to repeat history with the newly-named Multiverse Saga, as Kang the Conqueror seems to be the looming specter over the next few phases. Avengers: The Kang Dynasty is set to round out Phase 6 and effectively end this next era of the MCU. It seems like a similar situation to the one with Thanos, wherein the bad guy that's been behind everything the whole time is finally confronted by the heroes. As long as Marvel manages to do this carefully, and if they ensure that they don't simply copy their previous formula, this could be a smart idea.
Obviously, no one knows for certain what direction the MCU will be taking Kang yet. It's likely that his arc won't be exactly like Thanos's, since he's already had a major appearance in an MCU property (rather than just cameos in end credit scenes). Though he wasn't called Kang the Conqueror in Loki, a version of the character — He Who Remains — still played a big role in that story, and it was clear that the MCU was beginning to set Kang up as the next threat that the heroes might face. Of course, none of this was confirmed. It was only theorized based on Kang's role and importance in the comics, as well as the fact that he was also set to appear in Ant-Man and the Wasp: Quantumania. This led fans to believe that he had a much bigger role to play in the MCU.
It seems that this hypothesis was correct, as Marvel announced at this year's San Diego Comic Con that the final Avengers movie in the Multiverse Saga is going to be The Kang Dynasty, which all sounds like a lead-up to him being the big, overarching villain of the next era of the MCU. It hasn't been explicitly confirmed, but Marvel has been hinting at the importance of Kang going forward, so it seems like they're looking to do a similar arc to Thanos. Importantly, however, it seems like Kang will be more directly involved in the events of the MCU than Thanos was, which will make him dynamic in a very different way.
Rather than being a threat that looms in the background and plots behind the heroes' backs (while still being known to the audience), Kang will likely be much more present. He might be a constant source of tension and conflict for the heroes right from the get-go. This will present a very different challenge for the Avengers than Thanos did, as they will likely have multiple confrontations with him, and perhaps even with different versions of Kang from different universes. This will make their conflict more personal. It will allow for some more emotional stakes when they're fighting with someone that they already have a connection to in some way or have seen before, rather than a giant threat that they're meeting for the first time.
Thanos was intimidating because of his sheer power, as well as the size of his army. Even with the use of the Infinity Stones, the threat was more of a physical one, while Kang's threat is more complicated. The use of time travel and the multiverse extend the scope of what he can do, and he doesn't need the Infinity Stones to do it. The MCU has unlocked a whole new part of itself with the multiverse that is going to make the new threats and villains even more difficult to fight, which is a much-needed ramping up of the stakes after the Infinity Saga. Kang's persona and style are so different from Thanos that it's the perfect direction to pivot to after the success of the previous saga. After all, the last thing Marvel wants to do is become stale (which they're already being accused of by fans and those who are experiencing MCU fatigue).
If the MCU wants to keep things from getting stale, they need to ensure that they're making this new, post-Endgame era as different as they can. They've already been experimenting with form and genre, and so it will be beneficial for them to do something different with their main villain as well. Obviously, all of this is just guesswork, since Kang's true role in the MCU hasn't quite been revealed yet. However, it's safe to assume at this point that he is, in a way, the "next Thanos." The main advantage, however, is that now Marvel knows what worked and what didn't in the Infinity Saga. This means that they can hopefully plan this next era to improve upon it. At the very least, it needs to feel different. The inclusion of Kang the Conqueror should be just that, while still giving fans the familiarity of an over-arching villain like they've had in the past.