I believe that it is indeed possible to compare the premise of “Multiverse no Watashi, Koishite Ii desu ka?” with “Steins;Gate”, but only with the one specific part of “Steins;Gate”.
The beginning of Suzuha's route.
What made S;G dynamic as a story was that the MC actually interferes with the world lines. What made it actually fascinating was that Okabe performs experiments to understand the limitations of the machine, actually confronts a moral problem with changing the past, and uses that human-bending power despite knowing what horrible consequences it can have. That’s both engineering fiction (which is extremely rare) and a high-stakes emotional story.
If someone starts fading out of existence in this story, it will feel contrived (like in the S;G movie). If not, then the only stakes are that of any romance story, that the love triangle has to collapse. Only if they invoke the time travel / multiverse travel plot device can they reach another world line and fix the love triangle, which is a perfect opportunity both to nicely resolve the plot, and fill in the backstory behind the multiverse bullshit to make it less contrived, and make one of those cool cyclic plots like sending okabe back in time to make the world lines line up again. If we’re lucky we get an engineering plot too, but I’m not holding my breath.
There’s also the possibility of the harem end, where both girls accept each others presence in their relationship with the MC. At that point you might as well invoke multiverses again to get a bunch of variations of the heroine. Including the trap, because her mom ate extra protein in that dimension.
