What could Biden have feasibly done other than what he's already done in regards to climate change?

The free market already knows that the fossil fuel industry is rapidly dying, as evidenced by the fact that renewable energy is now the cheapest option for building out new power gen and oil companies have been diversifying away from oil for years now. Don't be surprised if you see Shell building offshore wind farms instead of oil drilling platforms soon.

He's included absolutely massive amounts of funding for renewable projects in the infrastructure bills that have been passed. Enough so that I expect the entire energy landscape of the US to look totally different within the decade. It can't be overstated how big of deal this is, and realistically, this is the most effective climate action he could have taken that wouldn't get stonewalled by republican obstructionism.

Re. fossil fuels and poor people, he's done a good job of both not handing more power to the fossil fuel corps while also not hamstringing the industry and subsequently jacking up the price of energy and transportation across the board. As much as I'd like to ditch fossil fuels, enacting policy that would jack gas prices into the double digits before we're ready to switch by gutting the fossil fuels industry would be political suicide.

Sure, a lot of the legislation he's passing hands money to wealthy corporations. Somebody has to build the infrastructure to get us off fossil fuels after all. That doesn't mean it isn't also improving the world around us at a pace faster than any president in recent history, and being in a position that Biden is bringing us to is a much more stable platform to build real social and economic change off of. There will be no need for a messy revolution if we can incrementally design and build systems that handle the issues we face in a level headed, evidence based fasion.