Entering a crowded market

I was brainstorming ideas and came up with something I thought had legs: SquareSpace for Online Courses
The customers would be people who want to teach something to the world through videos, and need a place to host their courses. The platform would host videos, handle their signups and payments, etc.

I did a search for online course platforms and discovered that there are already many options in this space.
Two years ago I would have stopped there, but now I see the existing companies as some validation that this is a good idea and people are paying for it.

I've read that targeting a niche, eg. The best online course platform for woodworking courses, or whatever niche is being underserved by the incumbent options, is a good way to enter a crowded market.

I'm wondering what other things I should consider before trying to enter a crowded space. How can I determine what section of the market is being underserved? Is there a better strategy than targeting a niche?

Thanks