From a technical standpoint
From a technical standpoint you are correct, EREVs are a dead end and it no longer makes sense to invest in them. From a consumer point of view they serve a purpose as a transitional vehicle. I agree that GM had to kill the Volt but I think they did it prematurely, it would have been nice if they had kept it around for another year or two.
I have a Gen2 Volt and a Model 3 AWD. The Gen2 Volt has a 100HP engine and better motors than the Gen1 Volt that you owned. The Gen2 fixed all of the problems that you described, it's completely adequate at highway speeds and I've had no trouble taking it on long, 2000 mile, road trips. It makes the perfect vehicle to transition from ICE to EV because it has no limitations.
With BEVs we are still living in a range gap period. In the summer the Model 3 is a vastly better car than the Volt in every way. With 310 miles of range and the Supercharger network you can go pretty much anywhere without inconvenience, I've done about 20 road trips in mine, but it does require a little planning which the Volt doesn't. In the winter the Model 3 has 200 miles of range which isn't enough for road trips. The Cybertruck will offer 500 miles of range which closes the range gap, 500 miles translates into 300 winter miles which is the threshold for a go anywhere car. When 500 miles is mainstream there will be no barrier to the acceptance of EVs. indeed we have a proof of concept, in CA, where they don't have winter, the Model 3 is now the number 3 selling vehicle just barely behind the Camry and ahead of the Accord.
The place where GM has screwed up is that the only BEV they have at the moment is the Bolt. They should have had a replacement by now. The Bolt nearly matches Tesla in efficiency, which is a major accomplishment when you consider just how terrible the iPace, E-Tron and Taycan are, but aside from that it's a very cheap looking car with not quite enough range and an inadequate charger. It's priced the same as the entry level Model 3, but it's simply not competitive with the M3. GM could have had a competitive car by now, they have the technology, but they've lost momentum. By the time they do have new BEVs the market will be crowded and they will be just another company. They could have been taking market share from their traditional competitors if they had stayed on their path, but they stalled so now the best they will be able to do is try and maintain market share.