> I don't understand how we're still using fossil fuels.

These fit an energy niche that can't be replaced with any one thing. China is just now investing in an electric military, for instance. Shipping will remain difficult to electrify entirely (which is surmountable, but certainly not in production). Coal and natural gas plants provide on-demand power that is not straightforward to guarantee with renewable sources. And there are many (likely almost all) grids that are simply not up to the task of transmitting energy that used to be transmitted by physically moving fossil fuels. Air flight has no renewable alternative as of today—though, I suppose we technically do have renewable forms of jet fuel, it's extremely expensive.

& of course we will need byproducts for the forseeable future for fertilizer, materials, chip production, etc etc.

It'll take a couple generations. Of course we should be paying poor countries to not use fossil fuels, but instead we're trying to force switching back to fossil fuels ourselves for no explicable reason (as an american obv).