Open world was a mistake. MEA lacks the subtle small things

Apart from Drack, Peebee or Cora, I keep wondering myself. These three at least kill the occasional enemy. Which is even more important, since most enemies make a beeline for the player. A nuisance that's not a Bioware exclusive, but prevalent in many games these days. Probably to create some false sense of urgency that reduces companions to window dressing.

Yes.
I am currently replaying the original trilogy, and shocked by how much Andromeda doesn't feel like a Mass Effect game. The series should not be open world, because it those off the pacing of the plot and general feel of the story.

It certainly feels like it. The most use I've had with companions in Andromeda is if I manage to get a shield boost from Cora. I've always viewed them as being there more for the company than aiding the fight in any way, although biotic combos provide a bit of an exception.

The biggest exception though was back in ME1 on Novaria, on the drive to Peak 15. I had Tali with me, and I was getting out of the Mako to shoot everything on foot for the extra XP. She went charging off after the geth, I was grumbling about companions going down in no time, except that time she tore through them all before I'd got more than a couple of shots off with my sniper rifle. I never did manage to get a repeat of that unfortunately.

Their weaknesses are more showing with the open world approach. Yet it had always been there. The statuesque NPCs, not moving one bit throughout the whole game. It was the same on the Citadel in ME2 and 3, it's more obvious with MEA, or DAI for that matter. The worlds they created are sterile and don't even rise up to Morrowind level, which was pretty static. It may have been even more obvious with DAI where your camp guards didn't even react when there was a fight right under their noses. Bethesda has other weaknesses, such as the NPC population not reacting to your achievements, but at least the NPCs pick up arms when there's an obvious threat.

I have as little hope of Bioware doing that as I have of Bethesda finally creating a NPC population not insulting you every step of your way. Bioware never had mobile NPCs. They always resembled telegraph poles. Bethesda always had NPCs not reacting to player achievements.

I admit that the exploration element in recent Bioware games adds a new level to the game, but I'm not holding my breath for them improving on that element.

Difficult. The Bethesda approach is technically more difficult (probably why people go on about bugs in Bethesda games, and it's the reason they have much bigger save files). The more open world it is the harder it is to fit in anything that really needs tight scripting, especially if you're not going to rather artificially close off areas until it's convenient for the plot to take you there. The Witcher managed that to a degree, but still had relatively telegraph pole-like NPCs a lot of the time, and nowhere near the degree of interaction with the world.

I'm sure it's all technically doable, but takes time and effort, and when you're owned by a company like EA who'd rather just crank something simple out frequently until it runs dry... Quality doesn't pay off well enough, alas. Every now and then something raises the bar enough (otherwise we'd still be playing games with low res 8 bit sprites), no doubt to the curse of some companies like EA who now have to put some effort in to stay in the race, and to the delight of others who relish the new opportunities, although the more complex things get the bigger you need to be to even stand a chance of exploiting them.

I'm not a fan of open world concept. Huge empty spaces that get filled with mostly second rate content. MEA doesn't do it better or worse than any other game, in my limited experience. So much time wasted in traveling

As with everything the extremes are always wrong. Outright eliminating open-world would deny us of the exploration element and would reduce the game to the shooting galleries of ME2 and ME3. I really don't want those back.
I admit though that also the open-world result in a loss of focus on the mains storyline and many players tends to become burned out and fatigued.

The best approach is something in the middle a sort of semi-open world which ME1 was.

ME1 made a clear cut separation between plot worlds (Noveria, Eden Prime, Feros etc.) and secondary quests worlds (all the others).

In the first type of worlds you really don't have open world exploration. You could of course explore hubs and the levels which were big, doing secondary quests in them connected with the main plotline and driving the Mako in some portion of it but ultimately the levels were still quite focused on your objectives.

The second type of world instead opened up and you could explore them at your pace doing the secondary quests and find random things, minerals and events to spice up the exploration there.

In conclusion they should do the exact same thing. Have specific designed plot worlds with focused narrative and limited exploration while on the other hand have a couple of optional worlds filled with secondary quests and narratives not related with the main plot. These worlds can be dedicated to resource gathering, full exploration and secondary questing.

This is my recipe to better integrate open-world in this game. We need it but it should serve the narrative and not viceversa.