Speaking as a student whose school primarily uses Google's suite (classroom, meet, etc..) but still has a few older solutions, some of which are free software, I can say that there's a common argument that schools should focus on pragmatism and working with what they have - the age-old argument that free software still is not accessible or easy to use. I don't beleive that this is still an issue.
Out of my current teachers and teachers I've had in the past, almost all of them were vocal about not liking Classroom or just didn't use it. It is basically a small layer on top of Google Drive & Meet that does not integrate anything nearly well enough. Most of my teachers seem to prefer Canvas, a free software solution to this, because it has more features. My teachers primarily cited the integrated quiz/test system as its biggest draw when I asked.
Classroom is also is very difficult for less-privileged students to use - speaking as someone who used to rely on a 4 GB of RAM netbook with a Pentium and was still using it for part of this quarantine, even with Linux things really get slow. This could primarily be attributed to relying on a lot of Google tabs at once (for Drive, forms for quizzes, etc) while Canvas I've never had to open more than a few maximum. My only other option is to buy a Chromebook and while my school can afford Chromebooks for every student, many students are relying on just using what they have.
With that, I don't think that the proprietary software really has all too much of an advantage in terms of pragmatism (which imo is even more important in schools). I don't think the usual arguments against adoption of free software really seem to hold up, though I assume that cost might be an issue that I'm not aware of seeing my district is rather rich.
I'd love to hear more teachers opinions on this. Hopefully this gave you an idea of how education tech is from a student user's endpoint.