If Google provided an option to disable AI search results, I'd happily turn it off.
I'd also happily turn off several other search features, more directly tied to revenue, which is probably why they don't like adding options. I'm sure their AI will be selling products soon enough. Got to make those billions spent back somehow.
At the moment it seems like you can avoid AI search results by either including swear words, or by using 'minus' to exclude terms (e.g. append -elephant to your search query).