What legislation like this would do is essentially let the biggest players pull the ladders up behind them
But you're claiming that there's already no ladder. Your previous paragraph was about how nobody but the big players can actually start from scratch.
All this aside from the conceptual flaws of such legislation. You'd be effectively outlawing people from analyzing data that's publicly available
How? This is a copyright suit. Like I said in my last comment, the gathering of the data isn't in contention. That's still perfectly legal and anyone can do it. The suit is about the use of that data in a paid product.
This issue has been noted since mastodon was initially release > 7 years ago. It has also been filed multiple times over the years, indicating that previous small "fixes" for it haven't fully fixed the issue.