A major time jump for ME5 is necessary imho
As others have said here on this sub, a 5th installment risks running the franchise into a corner. While Andromeda functioned perfectly as a spin-off with zero consequences on the main franchise's event, Mass Effect 5 taking place in the Milky Way has major in-game and metastory consequences.
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I've seen people arguing that the Reaper threat can't be topped without jumping the proverbial shark, and that low stakes are better to reestablish the universe. Therefore justifying ME5 taking place only 10-20 years after ME3, focusing on a low-level issue like the "Krogan civil war" hinted at by N7 Day posts, and allowing us to see the fate of characters we "know and love", such as Tali, Ashley/Kaidan, Garrus, Kasumi, Javik, and most importantly to solve the issue of the "breathing cutscene".
But this is Mass Effect. Not "Shepard and friends". For one, Shepard's story is done. Same for their crew. It should be allowed to rest, lest we end up with a Star Wars sequel trilogy situation where legacy characters weight too heavily on the story to be original. And for two, the franchise functions with major crises and high stakes. Low-level, fringe enemies act as a distraction, or as a side-story with additional quests.
However, the required level of high stakes cannot happen in the immediate post-ME3 galaxy. The lore is "solved". We know the root of the Geth-Quarian conflict and get to solve it. We know the root of the Krogan Rebellion and get to solve it with the genophage cure. We know (somewhat) the root of the Rachni wars and get to solve it with the last queen. Even if the player chooses the Destroy option at the end of ME3, the galactic social pulse would still border on happily-ever-after utopia for quite some time. Even a "Krogan civil war" wouldn't make sense only 10-20 years after the genophage is cured. The critical mass of Krogan population needed for something like that to happen (and to be large-scale enough to be an interesting plot point) would take much longer, considering that by ME3 they were bordering on extinction.
In addition, the ending of ME3 sees the Mass Relay network sustain massive damage from the Crucible (assuming that they are not outright destroyed because YOU didn't rally enough galactic forces for the final fight). Having the survivors rebuild the entire network across the galaxy would take considerable time, far beyond a mere 20 years. And a Mass Effect game where you cannot navigate even a fraction of the Milky Way in your top-of-the-line ship is simply not a Mass Effect game (Andromeda was an exception to the rule for self-explanatory reasons).
Hence the need to have a story taking place much later in the timeline, to make room for new stakes and conflicts (looking at you, Raloi and Yahg newcomers) and "soft reboot" with new lore for the codex about what happened in the past ~600 years. A game coincidental with the Andromeda timeline makes it perfect.
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A game taking place centuries after the events of ME3 works best if the tone changes radically, even more than what ME2 was to ME1. Andromeda took the gamble of giving us the same "awe and wonder" at discovering a whole new setting as ME1 did. Going back to the Milky Way forces the devs to tackle long-term consequences of the first 3 game events.
With ME3 now being 14-yo and ME1 being 18, fans have enormous expectations, because the trilogy is deeply loved. It is a burden and a shadow on any ME5 project. I feel this should be something that is reflected in the new installment, because something as important as the Reaper War would reshape the galaxy forever, especially around a figure like that of Shepard. With the centuries passing, it's almost impossible for them not to gain a status of civilizational hero, or that of a cross-species legend. This should be reflected in how the Citadel societies have evolved, from the imperfect "bliss" that it was pre-ME3, to a post-unity fatigue crushed under the weight of a quasi-mythical figure (reflecting what changed between the post-Cold War "end of history" of the late 2000s, and the post-NATO era of social tensions that the late 2020s are looking like).
Imho a setting 600 years later works best if it feels like the Citadel is a melting pot of civilizations living in the shadow of Shepard's myth, which creates profound fractures within all societies (especially humanity), along with new, deeper structural problems unveiled after the victory over the Reapers (for exemple, normalized military control and galaxy-wide martial law that never ceased after the war, and creates the need for outlets).
And the introduction of the Andromeda galaxy as a place that can now be reached (based on the "Andromeda distress signal" mentioned in past N7 day messages) create considerable implications for all species : a "gold rush" towards the new worlds, a release system for the pressure that would've been building with the hints of a Krogan civil war and life under the shadow of Shepard's legacy, potential tensions between the Heleus cluster colonists and the Citadel powers, and the whole ethical can of worms that the Angara's nature represent for Milky Way civilisations.
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The original trilogy asked: “What does it take for different species to unite?”. The future setting of ME5 needs to ask “What happens after unity succeeds ... and history keeps going anyway?”
Thoughts ?