There are other Firefish instances, though, in case one wants to use Firefish and also federate with mastodon.art.

There's Antennas, although they may not be exactly what you're looking for since they're in a separate location from your main feed.

I've read several people complain over the last year or so that Google's results have been getting worse and they add site:reddit.com or similar to improve the results. I use a search engine called Kagi that includes a "lens" to see forum results only which is neat. I wonder if this is Google's attempted answer.

Google has a bad reputation for killing its own products, to be sure. This is a part of Search, though, so I think less likely to die. If the results are terrible, and users don't click on them, I bet you are right!