Agreed. Exploration is an underrated feature in many games. People hear the terms "large environments" or "open world" and they just assume the worst and that the game lacks depth and consistency. This is patently false and some of the most successful games of all time (GTA, Skyrim, WoW, etc.) have proved that people love open world experiences and exploration. There is a sense of wonder and join you can gain from exploration and nothing else. In ME2/3 we were increasingly limited in what we could explore and see. I don't want that for Mass Effect going forward.
There is so much great material from ME1 that BioWare could revisit. As well as the integration of coop to enjoy that massive experience with a friend? Already an instant success. Not everything in a BioWare game has to be driven by cinematics and set pieces. Sometimes, it's just nice to let the player decide and make the decision rather than the game doing it.
People assume the worst because people have seen the worst. Consistently. Pointless collectibles strewn about the AC games, towers pervading every Ubisoft franchise, bugs and instability plaguing Bethesda games, and fetch quests littering the Hinterlands and beyond. Are any of these guaranteed to happen in open world? No, of course not but unfortunately, they are common pitfalls of the genre. While MENext has the potential to pull a quality open world (though, I find it unlikely given Bioware's history), It takes simple mathematics to prove that less covering area allows for more depth to occur. I think that's a very acceptable trade off. I can say with a decent degree of confidence that DA:I would have been better had its environments been cut down a little. It didn't need to be mutilated to the point of linearity, but a smaller scope helps maintain consistent quality.
I don't question the relevance of open worlds in gaming, but I don't think it's necessary in the Mass Effect universe. I may be skeptical towards the supposed benefits that going open world may provide, but I do not, nor have I ever, question the relevance of exploration in Mass Effect. It is absolutely imperative for a sci-fi game like Mass Effect to have some form of discovery. Contrary to what you may or may not believe, this can be achieved without wandering some landscape. Some of the greatest exploration I've ever done was in the confined rooms of Gone Home. Obviously, I don't expect MENext to contain the same level of minute detail nor the level of linearity required to achieve it, but it can strike a balance between the two.
Even if MENext were to have larger areas, why restrict it to only a few large landscapes? Why not have a large variety of smaller areas? Mass Effect is about the galaxy, it shouldn't keep the player occupied with one large region.
I too have grown tired of the needless haste Bioware has shoved into Mass Effect's pacing, but that has little to do with linearity. Once Bioware looses their obsession with grand wars with ancient evils, they'll begin to slow down. All open worlds would likely do is needlessly pad out the pacing with meaningless activities like hunting parties and tower raids which aren't characteristic of Mass Effect.
Smaller scope doesn't mean more cinematics and set pieces, it means more focus. Do I want Mass Effect to be on rails? Of course not, but a bit of focus can help keep the game engaging and consistently detailed. It doesn't matter if it's with a friend or not; if the game suffers from pacing issues or a bunch of padded content, the overall experience will be worse.