I feel like we're talking past each other a bit and maybe our experiences with external engines haven't matched up. I've seen whole platforms which were on the

I feel like we're talking past each other a bit and maybe our experiences with external engines haven't matched up. I've seen whole platforms which were on the milestones in the contract delivered in an incomplete and unusable state. I've seen engine developers prioritize high profile internal titles over licensees including explicitly telling developers that their features will be de-prioritized until they ship. I've had to implement non-insignificant features(ex: LoD geometry streaming) because it wasn't a 'priority' to support open-ish world games. While internal engines shared across studios may not have the same level of polish they can align with what the teams need and roll out large breaking changes in an organized manner. Once you have 2-3 studios using an internal engine there's a critical mass that builds around it(assuming game types overlap to a degree). Like everything there's pros and cons, however if I were evaluating a external engine in 2020 anything beyond what's present today would be a nice bonus and not something I would plan around.