If it's normal marketing stuff from something I had an interaction with -- clothing store, restaurant, etc. -- then I try their unsubscribe flow if it's 1-2 steps.

But generally, when I was using a Pixel I made extensive use of Google's SMS spam blocker and reported all of the random political texts that kept using different names. (And eventually Google's filter learned)

Now on iPhone (outside the US), there's no junk detection and I don't trust any app to not keep my texts. But I found that blocking a bunch of shady shortener domains + WhatsApp links with an app like Blocky[1] catches like 95% of them.

1: A power user app that lets you make your own wildcard & regex filters for texts. Offline and open source. Looks like it's delisted by now, but this was the link to it: https://apps.apple.com/us/app/blocky-sms-filter/id1535374786 . Maybe I'll make one to replace it when I get a Mac.