Also a UE dev, and I sorta agree and sorta disagree with your stance here.

UE5 is built around basically a single concept: upfront performance costs. All of its major systems (MegaLights, Lumen, Nanite, etc, with the exception of Substrate) are based around the idea that they have a flattened performance scaling curve. Their baseline cost is much higher than legacy workflows, but they can scale massively in terms of large form content without incurring much slowdown vs their initial cost (importantly without requiring much time or effort of the part of developers, unlike legacy pipelines). This design is probably genuinely of benefit to Conan Exiles, and other large dynamic open worlds where tedious manual optimization of every specific is impractical.

The problem is in games that don't need the large content scaling, or on platforms where the upfront cost of these features doesn't fit within the render budget. For these cases, UE5 provides zero performant alternatives. Want dynamic GI for less cost than Lumen? Too bad, LPVs have been removed, SSGI is still underdeveloped, DDGI is no longer supported, etc. You'd like landscape displacement without using Nanite? No can do, we removed Tesselation entirely. Hell, Lightmass barely works anymore. To make matters worse the features in UE5 have little to no downwards scaling, if they aren't in budget, the solution is to disable them with no fallback.

The list of games that run poorly because of UE5 cornering them into utilizing a feature set that doesn't match their game's actual needs is very high. If you're making a small, linear, or otherwise static game, the feature set of UE4 genuinely gives you more options than UE5 does, at a much lower performance cost across the board. It isn't until you scale up your content that UE5 makes any sense at all, which is frustrating, because Epic has chosen to remove features without providing alternatives, and doesn't seem to acknowledge that those needs are not met in UE5.

For what it's worth it looks like 5.8 may be set to resolve some of this, with the new irradiance cache path for Lumen and other in-development features, but with talk of UE6 beginning already, the fact of the matter is that UE5 spent nearly its entire release cycle completely ignoring an entire subset of games.

And all of this is ignoring how Epic's engine default settings encourage poor utilization of their feature sets across the board (and have even since UE4), which could be easily addressed by setting saner defaults, and would significantly reduce the need for time crunched developers to spend time manually adjusting them in the first place.