I'm pretty sure Unreal Engine will run into the same issue as Unity and RM games.
As things get more and more available, communities will form and grow, more tutorials and guides pop into existance, more assets will be created, more people will use it, and more shovelware will be thrown out into the world. I don't think it's a problem, it's just how things go.
People who like RTP in games will still play those games, people who don't won't. For me, the only sad aspect here is that the RTP assets lose perceived value as more and more shovelware gets produced, as it's already the case on steam, and RTP is by no means bad, it just loses uniqueness.
Though, I think with enough editing, you could still make a unique feeling RTP game, it's just more effort, imo.