Anyone else feel the dialogue was just generally more believable or interesting before ME3 and futur

And then what? Fiddle with the main control console, which I doubt even Spectres can just do willy nilly in full view of everyone, and then hold that position until Soverign actually docks with the Citadel. Him and a few commandos against the entirety of C-Sec and whatever other military personnel might be stationed there who may be drafted to help. And if he fails? The organics are now on guard, they'll begin investigating in earnest and Sovereign just lost its most influential puppets. I don't think so.

I don't know where you get "all knowing" from. Even at the height of their mysticism, the Reapers were never once referred to as omniscient. Sovereign sent the signal, got the wrong response or maybe no response at all. I don't see why he should "magically" know that the Protheans screwed with the keepers who then refused to listen to the signal. So yes, troubleshooting is required. The end goal may seem simple but trust me, when dealing with complex systems the cause can be anything but. It would also appear that it opening the dark space relay at that point requires a Reaper or specially designed creatures like the keepers  (who are no longer an option). Otherwise you could make the case that even with the Conduit once Saren's in the tower why doesn't he just open the relay directly instead of doing the whole thing with opening the arms and closing them once Sovereign's in.

Of course, you could make the case that the whole keeper plot is dumb anyway because why would the Reapers, hyperintelligent machines then rely on weak, inferior, designed organics to operate the most crucial piece of their technology. They should've set it up to beam teh signal directly, or better yet, not bother with a signal at all, and have some sort of presence on the Citadel already that just opens it when it's time. You know... kind of like they ended up having in ME3...

But then you wouldn't have a game, you'd have a short sentence along the lines of:

"Once there were a whole bunch of aliens living peacefully on this space station, until one day giant robot cuttlefish popped out of nowhere and killed them all. The End." It's the same with why the relay network isn't immediately shut down when the Reapers get here in ME3.

So yeah, there's been stupid things and plot progression because idiot ball since the start. Just at different points than you think. The idiocy was written to allow plot but if you accept the initial idiocy the rest of it mostly works. Not much of an endorsement but meh.

The problem is, you can let the initial idiocy go to just enjoy a story, but when they continue with the same sort of dumb writing it gets more and more glaring. Like I said above, ME only works because they built in a really stupid way for the Reapers to operate- using the keepers instead of a direct connection to the Citadel, or actually having the vanguard/monitor on the Citadel the whole time. They also gave Saren an initial idiot ball- attacking Eden Prime as opposed to just quietly going in and taking the beacon. That's where subterfuge would've done wonders over charging in guns blazing. If Saren had just shown up in a nondescript transport with an asari matriach and some commandos and told them he was taking the beacon for the Council, no would've batted an eye. Nihlus and the Normandy crew would've shown up, gone wtf?, Nihlus would've called it in, the Council would've called Saren asking why he got the beacon, Saren could've made up some bullshit and told them he was en route, then disappeared with it, maybe even stage an accident or geth attack and boom- zero suspicion, no Shepard on his tail, no one would've been the wiser.

But then again, we wouldn't have a story. It's not the best way to write, asking the audience to accept illogical things, but if you do it, and the rest of the story works and makes sense you sort of get away with it. The problem is in the sequels there's more stupidity that's on the same level. "Ah yes Reapers", the Collectors and the TermiReaper, the implausibility of Cerberus, Shepard's herpaderp jail time and when the Reapers finally get here, the focus on Earth, the relays still being operational, the deus ex machina right under our noses as well as a literal deus ex machina for the Reapers again literally under our noses. That last is the worst of the bunch because not only is it monumentally stupid, it compounds the stupidity of the initial dumb thing we had to accept to kick the series off in the first place. So that's why the flaws in the later games are more glaring and more often pointed out. It's not fundamentally worse stupidity, it's just stupidity compounded.

As for squadmates, replaying ME1 now and conversations with them don't seem to be markedly different from later games. I can tell when they only have stock phrases and repeat information vs after you've just done a major story mission and you can now progress to the next stage with them in all games. And please Garrus in ME1 vs ME2? In ME1 you can mentor and shape him into essentially a version of you (which the later games mostly ran with) vs ME2 and its infamous calibrations. ME1 Garrus also gives us the proto loyalty mission with going after Dr. Saleon. As far as I can tell it doesn't impact any variables practically but you could tell they used that and ran with it in the sequels. Tali and Liara  did have most of their initial conversations be a guided tour of their species, but it was the first game and thus the first opportunity to learn that stuff. How many other quarians or even asari do you meaningfully interact with in ME1? Even in the later games we learn nothing new about the asari's culture or society until Samara. And speaking of, Samara in ME2 and Miranda serve the same purpose initially, exposition on justicars and Cerberus respectively. As for ME3, while squadmates conversing with each other was a nice touch, I'm not sure the cost of less fleshed out conversations with the player was worth it. Everyone became click to talk unless they had a new major thing to talk about or at best you'd get a "walk by" convo where a click to talk would turn in to a few autoreplies from Shepard as well. I hesitate to call it an improvement.