Did you miss the part where I said "Discussions isn't MediaWiki"?
Blogs are a MediaWiki hack. Old Forums are a MediaWiki hack. And that not easy integration of Discussions into RC would be another MediaWiki hack. Discussions are deliberately not another MediaWiki hack.
Only threaded discussion features have been confirmed to be retiring. Everything else is to be announced at a later date. In fact, they have yet to release information about the retirement of features other than Forum.
Fandyllic, I totally agree with you. However, this particular discussion has already been had multiple times and I seems that we aren't going to be able to persuade FANDOM otherwise. I even tried giving them a starting point for getting wikitext in Discussions but they seem to have already made up their minds on that issue.
It depends on your perspective. The way I see it, Discussions is secondary to MW. From that perspective, if something breaks because of MW upgrade, then either the integration needs to be fixed (as opposed to modifying MW) or dumped. They have already shown that they are willing to dispense with helpful features in exchange for MW upgrades. If the integration has to be dumped at some point, it would just be another one of the casualties.
Creating a feature separate and not really integrated with MW was a choice and the problems with that choice are not a technical barrier. They may be a dev deficit in FANDOM, but that isn't a technical barrier. A technical barrier would be designing something that has an near impossible requirement, like needing a terabit bandwidth internet connection to be usable or something like proprietary digital right management that you don't have a library for.