I'm sure Larian would have preferred not to have any middleware problems, but that kind of thing happens in development. When the Linux engine was done, the choice was to update it to the outdated release version, or update it to the current version (Enhanced Edition). You can prefer something else, but those were the only options.

I don't know what version of OpenGL support will be needed.

The number of people potentially effected by the change in requirements is relevant to the discussion.

Saying everyone will upgrade sooner or later is entirely accurate, entirely practical and entirely reasonable. It is based on my own experiences and everything I've seen with computers over a very long time.
I have been unable to play certain games, and them many games, due to having an old computer. Even at the time, I knew I would eventually be able to play them. That is in no way condescending.
You don't need to be rich to have a computer that can play D:OS, or the EE. If you need to save to be able to upgrade, next year there will be more powerful computers for cheaper than this year, same for the year after that. Buying a console may also be an option (I bought an Xbox 360 on a boxing day sale before Divinity 2 was released, when an unexpected expense meant I couldn't get a laptop I had been saving to buy).

How is having a video card with DX 11 support (ie made in the last 5 or 6 years) equivalent to needing a $100k car? A 5 year old computer is typically low end; a $100k car is rather on the high end.