What you’re generalizing as “inverter power sources” don’t have any fundamental technical limitation like you describe. Those limitations are an artifact of the historical default of a “grid following” inverter that was suitable when the grid was mostly turbine and hydro generators.

Grid following inverters assume the existence of a certain critical mass of large spinning wheels as power sources to set the baseline frequency for the grid, and when those are lost can lead to brownouts as the follower plants are forced to go offline in response.

But newer solar plants can be designed with “grid forming” inverters which completely replace the role of spinning mass with a computerized vs mechanical baseline for the grid.

You can absolutely have a 100% “inverter based” grid as long as there are sufficient grid forming inverters within the mix. This wasn’t a problem until relatively recently when solar adoption exploded thanks to falling costs, and so the additional complexity of the technology wasn’t actively demanded by the market but that is no longer the case.

https://ffdpower.com/grid-forming-vs-grid-following-pcs-what...

https://www.opal-rt.com/blog/grid-forming-vs-grid-following-...