A release is a release and asking for better quality in said release isn’t crying out loud. Regardless of if it’s free to you doesn’t mean it’s free to everyone as enterprises are indeed both contributing back to source and waiting on PRs (thousands of them at this point) to be pulled.
You can’t have your cake and eat it too and call your product an “early release” when just because it’s a .0. Poor quality in the past also doesn’t justify poor quality in the future. I’m sorry but I fundamentally disagree here. I love this engine and as a licensee I think it’s fair to ask for some accountability and quality standard no differently than my customers ask of me.
If status quo was a defining metric to set standards, then improvements would always falloff linearly and this time next year .1 minor releases would be “fine” to be riddled with bugs, broken swarm, failures to build to certain targets. Just because someone shows tough love and is a bit critical doesn’t mean they have ill intent.
I think the OP was clear in stating if it wasn’t ready to come out of preview then it wasn’t ready to be “marketed and pushed” as a binary release. As a lead engineer that pushes software for a very reputable company, I can also agree that this would have never pass our end to end or functional testing pipeline. Thus, wouldn’t meet quality standards and leadership would indeed be asking questions and holding principals accountable.
As far as running older engine versions go …. It’s good advice but that is a result of “status quo” or a drop in quality rather than the desire of epics licensees. I promise you if a poll was taken on expectations of being able to take a “release” to market without cherry picks or major source modifications “like many ue4 versions were capable of” the results would ask for higher quality standards and stability…. It’s a reasonable ask …. Let’s be real here 
when you love something you want the best for it. This means you set standards and expectations and try to hold it/them to it. Otherwise, it’s counterproductive to the goal of a good product and trust from the customer/licensee ….it’s not entitlement … it’s a contractual agreement and partnership that adds value based on quality.
The engine isn’t “free” it’s “source available” so complacency around this agreement? … nah …I’ll never be able to get down with that. Sorry …. but we can all seek to strive for better and should. I’m experienced enough in ue5’s lifecycle (I’ve been in the epic camp since udk) to know better like you stated not to push anything to a .0 release but I’m also experienced enough to know it hasn’t always been the way things are today…. I’m also intelligent enough to know complacency and acceptance can sneak up on you in the worst way. Professionalism is being able to accept feedback and complaints as well as compliments and course correct.