Yes for all 301 D1 schools that is correct. Lots of offers and spots remaining. If the goal is to play at ANY D1 college level, yes lots of spots left. The numbers are with you.
If the goal is to reach top 50 (D1 or PG or whatever you want to use to rank), they're practically full for 2021.
If you expand it out to Top 100, then yes some have a few spots remaining based on average class size.
Not saying it's impossible, but that it would be prudent to get ahead of it. They typically have to see you play in order to invite to camp (unless bulk email auto response to a questionnaire (Duke and others)).
Go to PG events this summer. Attend some camps. Tryout for Area Code for further exposure, but you had to throw above 90 as a 2021 this summer to be kept. They didn't keep a single pitcher less than 90. Command didn't matter, that was obvious.