Should this game have been open world

No. Exploration in sci fi universe sounds great on paper, but then you're stuck on big, empty world. What do you fill it with? So we end up with poor man's Far Cry and explorers who travel 600 years to another galaxy to drive around in a jeep and slaughter local fauna.
Gimme galaxy map full of mysteries to discover ( that you can zoom in/detect, jump in space suit and discover) , derelict spaceships, first encounters with new species, full Star Trek mode.
This was a great opportunity for new direction away from overbearing plot...but they chose the wrong type of exploration.

Funny how Zelda BOTW is just as empty yet has better scores and is overall subjectively more fun to play.  I think it's just about execution of the mechanics and not due to the fact that it's open world.    

Should a scifigame be open world? Yes.
Should MEA, as it is now, be open world? No.

Open world needs sandbox elements and the only we got in MEA are random encounters which happen so often, they get annoying.

Absolutely not, open-world is holding back the genre.

It should be ME1 type of open world.

Or KOTOR type.

ME1 type would be better overall, but KOTOR type could work as well...

...but it should be ME1 type of open world.

Yes.

This is why I have such a big problem with this game. Because, you know, I actually expected everything you wrote. Full Star Trek mode. I thought WE were going to be responsible for the first contact, I thought there would be more species, even non sentient ones and we would decide (upon making an outpost) if we want to co-exist with them or slaughter them. I thought there would be much more interesting places to explore (yes, Vaults are cool, but I was thinking more about "natural" parts of the environment). I actually had some hopes that ME:A would be what No Man's Sky partially wanted to be in the first place, just limited to smaller amount of planets.

What's even more bizzare is that my expectations didn't come from thin air - that's actually how I understood all the game announcements. Yes, english is not my native language, but I think it's OK enough to understand basic sentences, and these sentences gave me the above image in my head. I think that this is my greatest disappointement when it comes to ME:A. I didn't mind the fetch quests and open world aspect in Inquisition because to me the world seemed more realistic, more life-like, especially The Hinterlands. In Andromeda the world is a big no-no and there's no hope for fixing it (unless the game becomes mod-friendly on Skyrim's level, so we'll see mods with new places to explore - 99,9% not going to happen).

Honestly the open world shit wouldn't be so annoying if it wasn't littered with fetch quests. Hell, I'd be happy if the length of the game was cut in half in favour of some interesting, high quality quests rather than go to X, scan Y, travel to Z and so forth.

That's not really the choice they had at design time, because they were operating with a limited budget.

It was a choice between a smaller and shorter game that was entirely content dense, or a bigger and longer game that included a lot of optional 'fetch quests' on relatively expansive levels (planets).  Taking out those fetch quests and the open world, wouldn't magically give Bioware the funding to fill it all up with lots of rich content, it would just mean Mass Effect Andromeda would be Mass Effect 2 done again - three or four hubs, and a couple of dozen missions to be completed in a more or less linear fashion, and it would all be over in 20-30 hours. I'm glad they decided to try something else, like they did with Inquisition.

I actually enjoyed roaming around in the Nomad, it was fun.

If they had reduced the number of small random encounters & find x items quests, & instead had more large extended combat areas like the Flophouse, it would have been better.

Yeah, similar to the planet exploration in ME1, the planets in MEA made the Helius Cluster feel big. ME2 could be more linear than ME1 because ME1 had already set the universe up for us and had already made the world feel like it was big. I have some critiques of how the open world was done, but I think the game needed to get the sense of exploration across.

I'd have no issue if MEA2 was a more linear experience because MEA has already set up how expansive Helius Cluster nicely.

Just because something wasn't implemented well doesn't mean it was a bad idea.

It would have been easy to make it work. I assume we got desert and ice for the most part because the game couldn't render forests, jungles, or other types of areas given the speed of the Nomad. No coincidence the more detailed areas like Havarl and Habitat 7 were no Nomad areas.

Solution - Have different types of areas on a planet. Parts where you can get out of the Nomad and explore other areas on foot. Better caves, descents into subterranean caverns, pockets protected from the scourge like the cave on Habitat 7. Would have made you want to explore the worlds rather than just driving over endless sand and snow looking for markers.

The quests didn't make much of a difference in anything, they were just boring fetch quests with a lot of system hopping, and the cutscenes made them even more tedious.

Solution - Give the player control over how the settlements grow, and actually have the settlements change as the game progresses instead of a generic viability number. Part of the story was colonization, let players see tangible rewards from the quests.

Example - Colony tells you they don't have enough soldiers to secure the colony from the Kett, recon and guard the survey teams. You volunteer to escort a survey, or better yet you get to pick rather escort the team or recon the Kett base. You either get intel that lets you destory the Kett base, or research that helps the colony make advancement, growing the colony in different ways.

It would have been easy to make the quests and colonies tie in the colonization aspect of the story, and not have so much system hoping because the quests would have been confined to the planet you were on for the most part. They just didn;t do it right, but by no means was a semi-open world a bad idea.

Now if you want to make a poll about whether you think they can do a good open world game, that's another thing altogether.

I hope they never go back to the ME2 approach.  Get dropped off at the back door as if these places have to security, run in and fight through some linear corridors, come outside and get picked up, rinse and repeat.