> Is that really so much to ask?...

Yes. You cited requirements that to be satisfied together require a huge effort. You want something that can "just work" and is also cross-platform, power user friendly (LaTeX), and should be snappy to be able to gain traction. Not to mention that you have to compete with the ecosystem lockin of Office-Teams-Onedrive-Sharepoint-Azure.

I frankly see no way a competitive alternative could appear without a billion dollar budget backing it.