How dare them wanting to make money. Seriously this is fine, if you are not happy fork it and maintain it yourself. AFAIK this is the whole point of open core. What you are asking here is that business to support code for free that reduces their revenue. Code is a liability most of the time not an asset.
I think the problem is the terminology. People grew up when open source software was also free. Open core uses the same terminology, although products are only open and free in a limited way. I don’t want to assume intend, but many users are mislead that way.
The difference is that older generations understand developers have bills to pay.