There is no need to reinvent any wheels by making a homegrown LMS. Moodle exists and is completely open source. Lots of large institutions use it. Even in the case that you need to do something really weird with it that isn't solved by one of the many plugins that exist, you're already 90% of the way there with its base platform, and only 10% remaining for DIY software development.
My university (a very large state school) transitioned from Moodle to Canvas while I was a student (2016-2020). They transitioned because Moodle sucked. Profs hated it, students hated it more. Basic things were difficult to find.
A lot can change in 10 years, sure. Maybe Moodle is better now (I doubt it). I'm all for self-hosting a LMS. But, can we at least self-host a good one?
Moodle also scales to pretty large schools, I work on an instance that is over 27k students. Integrates with pretty much every platform, authentication, etc.
And it's pretty easy to customize which is nice.
Throw it in an auto-scale ECS cluster and you have something that goes from 100 students to 20k easy.