1 or 2 GB of RAM? Yeah, that would've been the problem. Old CPUs can handle more than people think but there's absolutely no getting away from modern memory demands.

Yeah. 8GB of ram is pretty much the minimum usable amount these days. If you can get 8GB into an older machine (with an SSD), then it should work fine.

But 4GB? Pass.

I have a Lenovo Chromebook with 4GB and GalliumOS and it is still very capable with the latest Firefox.

With the right distro, 4GB with just a HDD is quite fine for Chromebook style usage.