Or just grid forming inverters?

https://spectrum.ieee.org/electric-inverter-2667719615

These do not address the concern of fault current handling. This is a much more localized and severe condition than frequency deviation. Think about dropping a literal crowbar across the output of a solar inverter. This is a situation the grid has to deal with constantly.

I'd argue that nothing that uses semiconductors would be suitable for the task. They get you to maybe 2x rated current capacity for a meaningful duration. A spinning turbine can easily handle 10x or more for a much longer duration.

We could put so many redundant transistors in parallel that we have equivalent fault handling, but then we are into some strong economic issues. There's also no room for error with semiconductors. Once you start to disintegrate, it's all over ~instantly. There is no way to control this. A synchronous machine can trade downstream maintenance schedule for more current right now. The failure is much more gradual over time. A human operator can respond quickly enough if the machine is big enough.

	▲	ViewTrick1002 31 minutes ago \| parent [-]
		Grid forming inverters provide 1/3 to 1/4 the fault current of a similarly sized generator. The other trivial solution are synchronous condensers. Or just let the generators and maybe even turbines of future emergency reserve thermal plants spin with the grid without consuming any fuel. Just ensure the proper margins exist in the grid and call in ancillary services as needed. No need to make it harder than it needs to be. https://spectrum.ieee.org/amp/baltic-power-grid-2666201539