Linkara covered the issues with OMD in greater depth in his review of the comic so if you want more detail go check out his review on it but the long and short of it is this; Peter gives up everything to try and save Aunt May from death for the umpteenth time and sells his... marriage to the Devil to save her. This is a story so bad that we're STILL dealing with the fall out right now as Peter and MJ have still not remarried and every attempt by writers who want to undo this mistake have their hard work undone the moment they turn their back for more then 2 seconds.
Anyways the core problem with OMD is that it wanted to regress Peter's character arc and does what it can and continues to do what it can to keep him from advancing. In this case OMD eased or altered everyone's memories of Peter and MJ ever being married and in 15 years it has still not been undone.
Just for comparison when the New 52 was launched DC basically divorced every major married couple and most of the minor ones too. About 5 years after the New 52 DC started to undo this and characters were remarried. DC has a little more guts then Marvel as one of their flagship characters got remarried after half a decade where as Marvel refuses to let their flagship character get remarried after a decade and a half.
And again the problem here is Marvel did everything it can to make undoing the deal with Mephisto near to impossible to undo without a LOT of baggage.
What makes me like the ending of NWH is that it gives us hope that Peter will find his way back to those he loves. While everyone's memories of Peter and Spider-Man being one and the same is hard to undo they left hope that it can be done. MJ still has the bracelet that Peter gave her and she and Ned are still out there and all Peter has to do is talk to them. And at this point it makes sense that he doesn't want to do that because in the span of a few days he's lost his aunt, his girlfriend and best friend was almost killed and he nearly murdered someone in revenge and it nearly cost the life of another version of himself and nearly destroyed the multiverse.
After that it makes sense that he would think that his loved ones would be better off without him in their lives.
Again, this isn't the end, there is still hope for Peter to get back with MJ, to regain his friendship with Ned and balance his life between Peter Parker and Spider-Man.
One thing I've enjoyed with Spider-Man in the mainstream series (those being the MCU, the Insomniac Marvel Universe and the Spider-Verse) is that there has been an active effort to let Peter grow up. May has died in 2 of this series and moved on with her life in another. Peter is either in a stable relationship with MJ or married to her and has a kid in one continuity and there's a good chance he and MJ will be tying the knot and likely will have a kid in the PlayStation Games.
Even the MCU took the conscience effort to not repeat the mistakes of the comics and has at least setup for this Peter to move on with his life and allow him to grow up.
And that's why I honestly kinda like the shitty ending of Spider-Man: No Way Home.
