I think compared to the Superhero cartoons of yesteryear there isn't as much focus on playing the "long game" or building up to stuff anymore.
Granted, to some degree we will be getting that with certain characters here (Harry, Otto, probably Norman).
I think it's also telling that we still don't know who Venom is yet so there may be more to this story then this 3-episode Symbiote arc.
Well, I think Marvel wanted a relatively more "back-to-basics" Spider-Man cartoon to tie-in to the movie but they also wanted to promote the other Spider-character despite the lack of connection between them and Peter in the comics.
So as a compromise we have Peter starting out as a solo hero juggling a double-life but we'll also have the other Spiders popping up in relatively major roles as supporting characters and other Superheroes.
To have a new cartoon to tie-in to the new Spider-Man movie. That seems to be the bulk of the reasoning behind it.
I've noticed this trend and it's frankly disappointing that current gag/comedy cartoons are playing the longer game better (or at least making more of an effort) than modern superhero cartoons. I had no trouble paying attention to longer, ongoing plots when I was a kid, and I don't think modern kids have this issue either. I think Marvel has gotten what it was like to be kids once upon a time and now they're guessing what kids like because they don't understand what it's like to actually be a kid.
The 3-episode arc seems to be starting off as a Black Suit thing before finding its host so there's no way to tell who will be Venom or what form Venom will take. I'd like to think Marvel is done with symbiotes being overpowered sentient beings like they were in USM, but you never know, they might go that route again.
Now, the part I bolded above is where my consternation lies, and let me explain why.
The first three episodes of this show, while being better than USM, are still a disappointment to me, and in your post lies a rationale that I think plays a big role in why this show still doesn't work for me despite ostensible improvements to make it a better show.
They want to do a back to basics show. They also want to promote the Avengers and the other Spider-kids.
You can't do both of these things. You have to choose one or the other. And by trying to merge both, you wind up with the latter scenario, of it being an advertisement for other superheroes and other Spider-characters anyway. All of this extra stuff undermines the premise of it being Peter as a solo, rookie superhero, and ultimately makes it another take on USM just with a facelift.
By featuring the other Spider-kids and Avengers so quickly, they undermine their own premise of this being Peter Parker striking out into the world as a rookie superhero. By giving him other Spider-characters, Peter can't realistically act like a brand-new, rookie hero, or you will have disasters that S&P will have conniption fits over. So Peter will have to be a mentor figure long before he should be.
By having the Avengers cameo so soon, it reduces the emphasis on Peter being the center of his world, and instead makes it clear he's just a cog in a larger machine. Even if the Avenger characters ultimately give him the thumbs-up, it reduces Peter's agency, he has to rely on adult approval for his actions rather than try to figure things out for himself and dealing with his mistakes.
Hell, this whole concept of a genius high school also undermines Peter to a degree. By being surrounded by other geniuses, Peter is no longer special. He will soon be surrounded by three other Spider-kids in quick order. This also no longer makes him special. He's just another Spider-character, the leader of a team, perhaps, but ultimately he is not the lone, solitary Spider-Man. What makes him so unique; his intellect, his power-set, his relationships with ordinary people, this setup undermines all of that because it's all been stripped away from him. He's just another genius, just another Spider-character, and he's surrounded by other supers rather than standing on his own.
This cartoon has reduced Peter into being lesser than the sum of his parts, and I fear this cartoon has taken a giant step towards rendering Peter Parker ultimately expendable.
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