Sadly that's indeed how trademark law works - if you don't make even a token effort at enforcing your rights, they can become common names and effectively be lost.

That doesn't mean one should rabidly go after every single possible infringing use, obviously, which is what the infamous drafted Rust policy kinda did. It's one of those things that are just not black and white, because laws say one thing ("be harsh all of the time") and actual mores around enforcement say another ("leave people alone when they're clearly in good faith").