@Seisage - there is one aspect of hobbyists 'conserving' species that I feel you overlooked. That's education.
When I kept Zoogoneticus tequila for 15 years or so, I knew it was a dead end project the whole time. But I was able to generate other dead end projects, and quite a few people who got fish from me tried very hard to keep them going, as personal projects. I had a bunch of weird shaped old aquariums donated to me, and I oversaw a project with these fish in classrooms.
Eventually, there was a fatal inbreeding problem and fertility vanished.
But maybe, just maybe, it inspired someone, somewhere among those hundreds of teenagers to consider vanishing diversity. Maybe, someone will work with properly organized institutions for habitat preservation, or change. Maybe some of those kids will become adults who support real efforts. We live in times where collective efforts are devalued, but we'll have to start supporting real efforts at saving species someday.
I see our fish as a great zombie movie we get to make. They're the swimming dead, disconnected from their natural history. Every fish in an aquarium has been predated, and maybe bred like a farm animal for a different kind of consumption. I question my ethics keeping fish sometimes, but I give up - I have a carnivorous curiosity that feeds on other species just as the rest of my body feeds on mammals and plants. When I went fishing in Gabon last summer, catching weird unknown fish to bring home and learn about, as well as catching fish for study by a couple of respected scientists, I was a predator. I watched the Gabonese guys going out in the morning with old rifles to find antelopes, and then I cleaned out my net and joined the same process, except to feed curiosity.
I don't know if it's good or bad, but it is. This hobby has made me a supporter of projects aimed at habitat preservation, and of governmental policies that try. At one point in Gabon I got to sit in on an impromptu meeting with a government Minister and discuss the need to protect a river that was the only home of a local fish. I knew a couple of scientists who had just crawled out of a river and people like me meant nothing compared to the slick gold mining interests and forestry companies that will probably kill that river, but you give it your shot.
I hope that by seeing what we've destroyed, even in fishtanks, maybe people will ask questions and seek solutions. Maybe.