How can one above average game sink an entire franchise?

The reason DA2 got a sequel was: IT SOLD. It was cheap to make and sold well.

DA2 was just as mem'd as MEA, the difference is that it was mainly done by the "hardcore" gamers, instead of them + media + the general public (that was always kind to BW). It was badly received by such gamers and created a divide in DAO's fanbase (which CDPR was smart to attract).
So EA was happy enough to give them dlcs and planned an expansion, that then was cancelled and gave birth to DAI.

DAI was well successful for a lot of reasons, one was that TW3 wasn't yet released. I'm not saying it was the main motive, but people need to realize that after it was game changing to a lot of gamers. Certain BW flaws, that they ignored for so long, won't be forgiven by the general public anymore.

Meanwhile, MEA didn't have a small dev cycle and sales...yeah, we don't know but EA/BW response indicates they aren't happy.
The reason it's bashed and mocked is because it failed in many ways. Too many to listen here.

tl;dr. DA2 SOLD VERY WELL, EA WAS HAPPY SO THEY WERE READY TO GIVE IT ANOTHER GO. WHO KNOWS WITH MEA.

I just dont get it.

FFXIII was a horrible game and it got 2 bad sequels and the series is still going.

Maybe I can offer some feedback as an OT player who hasn't played a single second of Andromeda.

It may have been named "Mass Effect" but it doesn't particularly feel like Mass Effect to me. Mass Effect is the story of superhero and his/her sworn retainers on a quest to save the Milky Way. But these characters have no impact on Andromeda. And it's not even in the Milky Way anymore. So everything that I got attached to over three games has been washed away. Unless the gameplay was truly revolutionary, it just wasn't going to pique my interest; and it didn't.

Maybe the Andromeda characters are good. But I don't care. They aren't the characters I got attached to. It's not even the same setting I got attached to. And I don't mind having to adjust to new characters or scenery. My favorite game series, The Elder Scrolls, is built around a cycle where each protagonist (and almost the entire supporting cast) disappears after each installment. But I knew this going in, and I knew what to expect, and therefore this doesn't bother me.

But with Mass Effect, I got so invested into the series because of all the characters and the like, and Bioware washed it away to make way for a new game. Those characters were at the core of what made me a fan of Mass Effect to begin with, and so with them removed, I removed myself from having any real interest in playing Andromeda.

I sunk a lot of money into the OT. Not just three games and their myriad DLC, but t-shirts, knickknacks, and other such goodies. But not only do I not have any Andromeda merch; I don't have Andromeda, and I have no desire to even bother playing it. If Bioware had gone the Rogue Squadron route and said "We're still going to make the main series, but here's Andromeda, a neat little side story!" I'd definitely have gotten Andromeda and given it a chance. But with the essence of the main series all but gone, it feels like a waste of time to even bother.

Maybe I'm an outlier. I'm not the Lorax or anything; I don't speak for anyone or anything else as far as I'm aware. But I'd be willing to bet that for one reason or another, a good number of people just never bothered (and never will bother) with Andromeda for reasons not terribly dissimilar to mine.

It's mostly an engine issue. Gamebryo/Creation is great for radiant AI but kind of sketchy for a living, breathing "open world." Of course they might be making a brand-new engine for TESVI.

I wouldn't say that. ME3, including DLCs was quite a satisfying ride until the ending. To call that a disappointment would be an understatement. The original, I mean, not Mehem and getting rid of starbrat entirely.

Well, I cannot blame those fans... anymore.  I was so much looking forward to MEA that I built my current max spec'd machine last year anticipating this game.  I wasn't happy to see so many people bash the game early on as I thought I was still having fun and hoping people hung on.  It was when a long time ME3 friend who probably played at least twice as much as I did (me 2,000+ hours) in ME3 MP decided to quit MEA that made me think about why I was still playing.  It was OCD.  I was trying to max out my manifest, but the games were getting tedious.  It's too easy.  People were crushing gold within 3 days of the game release.  Look at my threads.  You can see me encouraging people to play gold because it's so easy, back in the 1st week of the game.  Once I maxed my manifest, I realized I really didn't enjoy the game at all.  I now no longer blame those who whined about the game early on.  My OCD blocked those complaints, but now I agree with them.  MEA MP isn't very fun at all.  My gold games started feeling like speed runs.  Guaranteed credits in 12 mins.

I don't know if we can entirely blame Mac Walters.  Maybe his heart wasn't in it.  If you read the Kotaku article, a lot of the blame goes to EA and the developers who wanted to do a procedurally generated world.  Neither No Man Sky nor Starship Citizen will ever amount to anything.  We'll look back 10 years from now and shake our heads at those two games.  Games need a good story.  I don't care how wonderful the combat or exploration is if I'm not drawn into the story.  Also, games need to be challenging, and the AI in this game is really not threatening.