You don't need to innovate on the foundation of your product. It's a game engine: If it fulfilled your needs when you started, it's fulfilling your needs now. With open-source solutions A) you can't have the rug pulled from under you, as you have a perpetual license, and B) you can fix/modify/add things yourself if the business needs arise.
With a proprietary solution, you might get A, but you have zero hope of B. It's an objectively worse proposition.
If my business is making games, I don't want to fix/modify/add things to a game engine.
You do need to innovate on the foundation if you plan to maintain your game long term: new consoles support, new hardware support, obsolescence of old platforms, etc...
You do not need to innovate if you plan to let your game rot and become unplayable 10-20 years later.
Yes having a FOSS solution for the foundation would be ideal. That was not the topic of the discussion. The topic was about the claim "we can fork if we're not in agreement".
No, as a game developer you won't be forking and maintaining a game engine. No a "just fork it" is not a viable solution in the majority of cases as you need a strong community behind you and your fork to make it last long term and not rot after 2 weeks.
Actually it's quite common for game dev studios to make custom mods to engines (source code to Unreal engine available here for example: https://www.unrealengine.com/en-US/ue-on-github). The idea with forking an open source engine as a game dev would not necessarily be to maintain it for the community, but to bring it in house and ensure continuity for your own projects.
That's fair, but if we consider the amount of game dev studio that have the resources (time and money) to do that, versus the amount of indie game devs and small studio who do not, I'm not sure that it's fair to say "you can just fork it".
The examples of successful forks are anecdotal, they are the exceptions not the rule. This is survivor's bias.
I can't think of a single example of an unsuccessful fork of a large project caused by a monetization change. So I am not convinced that success is the exception for that case.
> let your game rot and become unplayable 10-20 years later
Don't worry about it. Other people will literally solve that problem for you if they like your game enough no matter what you do. They won't even bother asking for permission.
With a proprietary solution, you might get A, but you have zero hope of B. It's an objectively worse proposition.