The main problem, I think, is that the extracurricular compilation material shows that latter-day Square doesn't actually really understand how to use or deploy the best themes of FF7. The compilation gets the flash and style right but the substance almost always misses the point of the original delivery and arcs.
The other problem is that FF7 is a weird, eclectic game, something it got away with both because of the era and because of its two unique art styles. There's stuff which will appear way more horrid and grim portrayed in a photoreal style and stuff that'll just seem silly af. Stuff will have to change significantly to make it all feel cohesive in a modern design, and obviously changes risk upsetting fans. Being different is fine, obviously, but at a point it becomes a clash of the two ideas - where elements of the original game that must be respected risk compromising the new stuff and the new stuff compromises the classic stuff. Cross-contamination.
Whereas the mission set out before RE2 was relatively simple - RE2 is a project with a pretty simple tone and style - FF7 is loads more complex. In this sense I think while fans are focused on the scale of the game and the being split into multiple parts thing, the scope of the project, actually nailing the tone and feel and not ending up feeling like a caricature of the original (something RE2 remake nailed) is actually imo the biggest challenge for the project.