"Open-core sucks" is a blanket statement as the incentives of the business do not align with the users of the project. And as a result, in my book it's a red flag for an open-source project, and I can't think of a single project I like which does this.
The incentive of an "Open-core" business is to convert people to the premium version of the product.
This has the effect of hindering/restricting development on the community/free-version, as it's vital that the community version needs to be worse than the premium version.
Almost any monetisation strategy has this effect on open-source though. Say for example consulting; if you're paid to help users setup/configure your project, then your incentive is to have people struggle with your project so they need to pay you for help...
As you can tell I'm a little pessimistic, but in my opinion almost any project that is open-source and trying to make money off it's users, has incentives that will negatively impact the project and it's users...
Hope this helps, I'm still open to projects which have any of these monetisation strategies, but they have to be of much, much higher quality for me to seriously consider.