Yeah, I'm not saying I'm on their side. We shouldn't be building at a pace that can only be enabled by new fossil fuel plants, correct. But the problem is the power plant, not the DC itself.
I'm also not convinced that gas/biomass plants are the only way. They're an easy way, sure, but solar these days is very cheap and quick to install. And these companies have a lot of money to burn! It feels like we have a great opportunity to force some very rich entities to build out renewable power and instead we're all wringing our hands about DCs sucking up water and looking ugly. It's all kind of a waste.
EDIT: Also, a big reason for the on-site power plants afaik is because grid/transmission construction takes forever. It'd be nice if we could actually fix that, perhaps with all this new money flowing in, but y'know...
As far as power plants go, to march the current estimates for data center demand over the next decade are astronomical. A large percentage of that power generation is going to be natural gas and biomass. You can’t really build these massive data centers on the timescale needed without them.
Is it stupid lump in a small data center with these massive projects? Yes it is.