Some reference of this discussion can be linked to these thread (inside there are thread reference links too):
https://forums.xonotic.org/showthread.php?tid=8529
Sorry if what I just wrote below is a bit long... But for something it is clarified.
At a certain point, you're right.
There are limits to the game as well as the engine has:
- You can't make a voice chat. It says there:
Voice chat within Xonotic will never happen (at least until / unless a Daemon-based port is available). Apart from the incredible amount of work involved, Darkplaces isn't capable of relaying that volume of traffic without extreme impact to gameplay. Since Discord (and Mumble to a lesser extent) are the de-facto standards for in-game voice chat, there'd been very minimal utility to implementing it anyway.
- Physhics are limited and still only can be used for experimental reasons. It still lags and suffers fps drops.
- Developing QuakeC code in Xonotic, you can't create more STATs by exceeding the limits, I think that are functions treated as bits of memory. If you surpass the number of STATs, it'll cause spamming errors and possibly shutdown the game.
- In certain things like assigning an attribute to an entity, it can be complex to solve. Also, it doesn't resolve in a moment, it can take days or even months until you realize something that you didn't know was what was needed.
- The process of developing something can take a lot of time and sometimes need to work correctly, cleaning bugs and code parts.
The development isn't easy as Unity and Godot as you think. Depending on what things you have to handle very carefully. Well, although this also applies to other games, but this one requires more effort to treat well depending on what elements.
On the other hand, you will find very few people here who seem to be used to trying things outside of the community and know things aren't from here. They've struggled with the old that the only thing they can do is slowly come up with workable solutions with this project. They have it difficult to put the project on the other engine.
Maybe they don't have enough knowledge to be able to overcome...
I don't see anything wrong with copying the assets and implementing it in another engine. But considering that, there are mappers here that have all the maps saved as .BSP format or some project of theirs (.MAP), maybe there is some way to pass these maps in another engine.
What I don't know is that why they complain about something new, they don't seem to try it afterwards.
It's like protesting a food you've never had tried to eat and you don't know if it is good or not.
I remember that there is a community that started to move the project to another engine about 5 years ago, they even put their old project as if it were a voluntary and optional process, everyone could do whatever if they want to use the old part to test optionally. But they are focused in the actual project (in an actual engine) than the old one (in an old engine).
Trying new things is like exploring the unknown, you can find things that you've never achieved and didn't know if something was possible to do it.
So it helps you open yourself up more.