IPv6 should have taken over as the standard at least a decade ago IMHO, but the way things are moving, I would be surprised if it has gained much traction (say >25%) for regular home internet connections 10 years from now.
Less than a third of the top 1000 sites are reachable via IPv6; the rest require IPv4. (The 30% capable of IPv6 are also capable of IPv4 and will be for a long time.)
The vast majority of home connections don’t offer IPv6 yet, so most likely the connectivity test you ran is entirely correct.
You’re perfectly fine without it as far as MSFS is concerned, several years from now as well.
The reason you’ve had those issues is most likely that Windows or some component thought you have IPv6 access and tried to use it, but since you don’t, all connections will fail.