That would be a terrible idea, not only because the Mass Effect setting isn’t built to take into account time travel, but like with Andromeda is a tacit admission that they wrote themselves into a corner with Mass Effect 3.
I’m very leery of time travel stories in fiction not built around the conceit, because like SF Debris says in his review of Star Trek First Contact, if it’s something that isn’t difficult to do, then why isn’t it used more often? Most writers tacitly acknowledge that on some level, yet they will still write stories where the addition of time travel to solve a problem or create a conflict, despite that in more details-oriented settings raise a lot of questions; to the point where you can almost break the setting thus destroy narrative coherence.
Let’s go with the rumoured time travel plot in Mass Effect: say they use it to undo the Reaper threat. How exactly do you do that? Even if we retcon the idea of the Reapers being a nigh-alpha-civilisation and say they’re only 10s of millions of years old, wouldn’t eliminating them cause the Galaxy to be flooded with civilisations that would’ve otherwise been reaped?
What if we just assume they use time travel to just stop the Reapers in the latest cycle? First: I don’t think Javik would be too happy about you throwing his people under the bus. Second: when do you stop them? Before Saren? That wold only delay the inevitable, given what the sequels showed us.
Before Sovereign started the Rachni Wars (pertinent part starts at 5:07)? That would have interesting implications for the development of the Galaxy, especially given the rules about opening uncharted relays and if the Krogans would even be within the galactic community. Just after the First Contact War? Sure…but it would be pretty difficult to convince everyone of the coming threat, let alone
fucking time travel existing.
Regardless of when they choose to go back to, just having time travel in Mass Effect would make things very messy, and would likely invalidate player choices worse than the Indoctrination Theory.
To make a very long story short, yes, because all the problems that people complain about began in Mass Effect 2: the focus on characters and romance over story and setting, humanity being special and human secret societies being more powerful than much older alien nations, simplified dialogue trees, much less focus on the knowledge quest aspect, and the throwing away of what appeared to important plot elements from the first game (the Rachni Queen, the cipher, Ilos, the conduit, Vigil, the Thorian, et cetera).