I’ll be the first to defend Epic, lol. Could you show us what your content is so we don’t blame Epic for something none of us actually seen? And you say, and I “How can well detailed objects up to 100k Tris be lacking of quality?” Is that maybe the problem? 100,000 tri’s? Is that REALLY needed? If I placed 10 in my scene, by my games “wiggle room for more assets”, I could place those 10 and I am tapped out for poly budget, not to mention the textures that also have to be drawn on a 100,000 tri mesh. Is said mesh small or big? Also could be your issue. It’s a sales pitch to Epic, not a “get my stuff on there because I and others think it looks great!”.
Also, is your mesh for ArchViz, games, production?! Not specifying could hurt your chances. If a 100,000 poly mesh is for “games”, Epic may be laughing at you behind a screen (probably not though).
Show us your content so I can also defend you 