I say they are not connected because there's nothing in any of the tv shows which will cause a ripple effect that impacts the film world despite the fact that an internal "one universe" logic would lead to that happening.

Let me explain what I mean: Once started the tv shows and films really just run on separate tracks.

Season 1 of Shield was written and conceived of with full knowledge of Winter Soldier and organically fit into that film. That's never happened again. You make a good point but I mentally intended to start after that season for this reason.

Agent Carter was a direct continuation of her character from CA1.

sure, Agent Carter is a tv spinoff of a movie in a way which has no interaction with the rest of the films. Given Marvel TV and Marvel Films don't interact it's a really smart move to make that show a prequel set during the founding of shield so the lack of future connections isn't a problem. I wasn't thinking about Carter but its a good example of how this could potentially work well together.

DD S1

Barely. You establish canonically that its the same universe but beyond throwaway dialogue there's no impact. But being the first show set in the aftermath of a pre existing background the problems are minimized. The real problems come later with e.g. Jessica Jones' Kilgrave plotline makes no sense. In a world where Thor exists, magic, mutated monsters (Hulk) and other metahumans its not clear why we are supposed to believe the public would see a smooth talker as crazy.

You can use the MCU to set up the founding stakes of a spinoff tv show without any problem but once the tv show starts going it's creating its own canon independent of the films and its very clear that the two don't work well together.