I did too, and I'm hoping ME4 is both a trilogy and Andromeda sequel at the same time. But if it's going to ignore all of Shepard's journey for the sake of not having to write around choices you could have made, it feels like it might as well be Andromeda 2 full stop. But i get that Andromeda 2 is a harder sell than Mass Effect 4.
I suppose that begs the question of what constitutes as "Shepard's journey" and the scope of storytelling it allows, alongside creative desire to forge new ground. The trilogy is rich with memorable content, I don't think I need to profess my own love for it any more than I do, but there's a real risk of creative stagnation when you're anchored too heavily to the past. I've criticised BioWare for this in the past; they need to ensure they're writing stories they want to tell, that inspire and motivate them, and not stories "for the fans". And as much of a fan I am myself, when you tether yourself too closely to the past you run the risk of endlessly pandering to what fans want to see and hear about instead of just moving on and telling new stories. And unfortunately I don't really trust BioWare, if in that position, to err on the side of caution. They're bad for fan pandering.
Funnily enough I ended up liking Andromeda like you, and one of my criticisms was how it haphazardly pandered to romantic ideals from the trilogy for no reason. Another Citadel, another Normandy, another advanced precursor race that disappeared, etc etc. All the while undermining its own unique premise and ability to act as a soft reboot.
So I can see why a trilogy sequel with a potential time skip would seem like the best choice. It provides a basis to leverage trilogy material in various ways that could be interesting (eg: who survived, the state of the galaxy and its various empires, the scars of war remaining, etc) that still fundamentally acts as a "sequel" but in the same breath distances itself away from specifics so you don't end up with fans getting excited just so they can see Garrus/Tali/Liara/etc again, or because they're desperate to visit Nexus 3.0, or because they want to see the fate of Conrad Verner. I've long advocated for a direct sequel, but I'm open to the idea of a time skip for what it can provide.
Liara would act as an anchor character too, a way to bridge the identity and lore of the trilogy over to a new story technically set in the same universe but some time apart. It's not unusual for writing to have a character like this; an old sage, ancient record keeper, etc. Some character that can serve as both a lore dump and an engaging identity, to personify a period of time that is now gone, and invite both familiarity and new. I can imagine BioWare are well aware that they probably still need to start a new story not too beholden to the past.
Because, and I don't want to alarm anyone, but by the time this comes out Mass Effect 1 ain't gonna be fresh any more. It'll be the beginning of a trilogy that was wrapped up two hardware generations ago. And if we ballpark a launch date, Dragon Age 4 in ~2021/2 and Mass Effect 4 in 2024/5, there will be 17 and 18 year olds picking up the new Mass Effect who were born the year the trilogy started.
EDIT: Also beyond the logistics of Liara being one of the few characters that could be alive, it'd be neat for her to be in that role. It fits her character's origin; an archaeologist who has dedicated her life to documenting history and unravelling truths. We meet her as someone devoting her life to Prothean history, namely their disappearance. She rises to the role of a person with access to the most information in the galaxy. And in the war's climax she's one of the few characters thinking beyond victory, creating the blackbox to ensure the past is documented in case of loss. Her being a central bridge between the old the new fits her identity to a t.
