The very fact "right to repair" had to be coined, proclaimed and we're fighting for it is a regression from the early days when repairing a radio wouldn't be violating some clause.
Of course, the openness was more accidental or pragmatic than really intended, and we saw companies slowly put up the barriers as they found technical and legal ways to do it (like forbidding plugging third party phones to the network for instance). If it's a frontier, IMHO it would be more akin to the battlefields front lines than anything else.
Put another way, the battle has always been social and legal.
It's true that malware authors are much better funded and more aggressive than they were a few decades ago, so we have some long threads talking about how there is an element of the paternalism here that's protecting people from some pretty malicious stuff, which could also cause a lot of harm. However, seeing this paternalism as the basic normal way that software is used shows that we've lost a lot.
John Deere has built a great tractor that the company itself prevents you from repairing without their involvement.
The only beneficiary of open source there is John Deere.
It is a failure. Things have been moving away from openness. A frontier would move toward it.
Of course we'd all prefer open printers and cars, but those domains aren't mainly limited by software ideology; they're limited by regulation, liability, and econ. The fact that programmers can build entire OSs, compilers, and global infra as open projects is already astonishing.
So yes, the world is still full of closed systems... but that doesn't mean FOSS lost. It means it's reached the layer where the obstacles are social, legal, and physical, not technical. IMO that's a harder, slower battle, not evidence that the earlier ones were meaningless.