The whole notion that the shows, especially Agents of SHIELD, didn't take place in the MCU has always struck me as not just foolish, but overly complicated. So what, the AoS universe is exactly like the MCU with all the same events happening at the same time, and all the same characters (played by the same actors), except Coulson's alive? That's far more complicated than it needs to be.
I get that people were annoyed the movies didn't acknowledge the shows more. That annoyed me too. But if you thought they were going to, then you weren't thinking it through. The pacing differences between film and tv are substantial, we were dealing with separate companies with their own contracts and schedules and budgets and audiences. That's a lot of hoops to jump through for minimal payoff. And how many people watch a Marvel movie compared to the shows? It's not in the films' best interests to waste time and resources establishing something from the shows when most of the movie audience don't watch the tv stuff. I mean, if they had Quake show up in Endgame, most people in the audience wouldn't have said "Wow, its Quake! How cool!" they'd have said "Who the hell is this and why is she here?" Fans like us would've loved it (and I really wish Coulson and Vision had been there for that last fight) but we're a vast minority compared to the general audience.
The films referenced the shows in more subtle ways that established the connection. It was a mostly one-way street but that doesn't mean there was no street connecting them at all.
The Defenders.....it doesn't really matter much if they were part of the MCU or not. The Mature rating on those shows was enough to make sure the only crossover was in easter eggs and "blink and you'll miss it" references. Disney doesn't want Daredevil showing up in Avengers just so little kids can backtrack that character to Netflix and end up with nightmares.
In any case, Marvel Studios being responsible for the streaming shows is going to give us the full-blown interactions the tv stuff wanted to do but couldn't. Keeping it all in-house smooths over most of the hurdles involved in crossovers.