Distances to the VA can be far for many. It can be extremely difficult to be seen by another facility/provider. It can be difficult to get/use your benefits in general. PPOs are basically the same type of restrictions, only the facilities tend to be held to higher state standards.
A lot of veterans live in rural areas. Far more than you’d expect. Anecdotally, literally 100% of all the ones I know, but definitely not all.
If you compared normal insurance and care options where they are at (especially considering their income level) to VA care, it’s actually quite good. Especially if you know how to treat them more like an HMO and work the system.
Private rural medical care is… not great.
And usually requires a lot of travel. And unlike the VA, is rarely in a single facility.
Generally everyone bitches about it though, because that’s how the military works anyway. And yes there are often (changing) systematic issues, though they often get fixed.
Are there better options? Yes, especially if you’re high income and can afford a higher tier private plan, and/or live in a higher population density area where facilities and standards of care can afford to be higher. That is not a typical situation for most Veterans though, for many reasons. And not a typical situation for a lot of the population either.