People inexplicably love ME1 despite a lot worse sins than DAI. The pointless collection quests. Boring environments. Terrible exploration and a crap ton of recycled locations - the same habitation on every world.
I found it incomprehensible. Every single flaw in DA:I is present - and magnified - in ME1.
It's the same mechanic, only one series (ME1) did it way worse. I just don't get it. I tolerated DA:I a lot more only because I suffered through ME1s flaws.
It's because they are different types of games with different types of plots. There is also a significant difference between what you do in the first part of a series an what you do in later parts.
ME1 had to establish its setting, technology, inhabitants, and lore. DA:I is working with an established setting. ME1 starts small and takes awhile for the story to expand into the larger mission. At Virmire, it expands once more. With Inquisition, while I don't know where the plot goes, you start out in a large scale war, do you not?
Things like reused environments can make some sense in some settings, but not others. They didn't work in DA2 because there's no reason different natural caves should have the same layout. They work better (though you don't have to like it) in Mass Effect when you think about prefabrication and modular construction. Also, the buildings that look the same on the inside also look the same on the outside, so it's clear they are the same type of structure.
I agree that the exploration wasn't great, but similar to complaints I've heard about Inquisition, the problem was that the maps were so big with so little in them, so you spent a lot of time trying to get the Mako over some weird hill just to find a few pieces of crappy gear.
Then, as was mentioned, our expectations certainly change over time
Agreed, no one seems to understand the invincible, unbeatable Reapers were the reason for the ME3 ending because they needed a way to stop them.
Well there was no need to set them up as so powerful, but even doing so there were other ways they could have dealt with it.
It is a horrible, terrible game. It is a terrible game saved by the setting, characters and plot. I love the game but decidedly not for any game-y element. It remains the only bioware game I can't play again because I can't face the controls, combat, lame exploration and game awful inventory.
I don't think the underlying game is as bad as you do, but you are right that the entire series is carried by it's setting and characters.