Miles Morales was disappointing on many levels, it ends up coming across as a decent DLC (and much better than the 1st game's DLCs in scope, but not in interpersonal NPC interactions), but not a full game.
Note that I loved Into the Spider-Verse, and was hoping this game would deliver the same enjoyment - it didn't even come close.
1. If it had come out BEFORE Spider-Man, I would have loved it. AFTER Spider-Man, it feels like a cheap knock-off of the 1st game with less enemies, a prettier city you have no compulsion to explore to appreciate, a cardboard cutout of a corporate antagonist, and a distinct lack of Spider-Man villains beyond shallow cameos - they even repeat one shitty boss fight with one of Spider-Man's dumbest (literally) villains.
2. The Roxxon enemies are less interesting versions of the Silver Sable mercenaries - even fighting them feels the same (well, except they don't fly). Their tanks even have the same Silver Sable turrets you can rip off and slam people with.
3. The story, on paper, is great and if I read a background summary of the Tinkerer, I'd be impressed. The dialogue and scenes, executed in-game, however, are shit and you can see where the scene and dialogue are going waaaay in advance.
4. Petting a cat and having a cat backpack is great. There are some minor cameos in flashbacks that are also great. Everything else is shrug-worthy.
5. The virtue signaling in-game is cringe-worthy - I'm all for diverse voices, but if the game is set up so the representation boils down to "HEY I AM DIVERSE," it just makes the story even shittier. (Best example is the homeless volunteer at Feast who every time she's introduced, she emphasizes she has a girlfriend, to the point where it feels forced - also, note that the homeless character has nothing else of interest going on about her except her sexual preference which feels shallow and insulting).
6. The SFX hunting quests were complete ass and frustrating. Photo collection in the first game was fun, the SFX sampling was the polar opposite of that. (I do think it was a good idea, but it was so badly implemented I wanted to yell at the designer.)
7. Miles' invisibility is great, it beats the Arkham Batman problem of having to find somewhere to hide until the enemies reset their patrol patterns - Miles' invisibility allows instant-hide and faster enemy encounter resets as a result, and I really enjoyed it.
That's about it. I hated the fodder enemies and thought Miles' new electricity powers were kind of out of place.