From my experience, there are all kinds of levels of bots. Add them all together and they can produce a ridiculous load on a site (especially a fragile one that you have to secure anyway). So I look at the volume, trying to block anything stupid I can get away with.
It is a game of whack-a-mole. It also can cut down the overall traffic to a fraction of the original, which has tangible infra costs benefits.
And yes, captcha works better in a lot of cases. Fortunately I'm not selling JA4, I'm just curious.
And yes, IP rate limits and ASN checks work really well in plenty cases. Side note: I got a high-throughput free offline asn-checker too! https://blog.miloslavhomer.cz/asn-check/