Innovate and Die is the utter slogan of today's times.
A decade ago it was similar, but today it's more valid than ever.
I'm a passionate Grammarly user, since the times when they were in beta (that makes 2016-ish?). I'm still using it, but if Apple Intelligence turns out to be that good as they market it, I will be seriously tempted to put these €144/year into a different use.
The good news (for me) is that I'll have enough time to test AI (Apple Intelligence), so that I can decide if I shall make the switch or not. But then, on the other hand, all "big" ones come with their grammar solutions (incl. Microsoft, for Office), so I don't see how Grammarly will hold. I hope some of the big ones buys them soon, as it'll be very sad to see them decline and go.