Give me an example of a finished, good adult game that has realistic, real-time 3D rendering like this one?
There's literally none.
The rare ones that tried are either in ABANDONED state or are still in alpha state after 5+ years.
Because developing an adult 3D game is a WHOLE DIFFERENT LEVEL of time and investment than any other game, especially the games posted on this site which are 90% RenPy/RPGM.
The vast majority of 3D games here are rip-offs which all reuse the same assets, low-poly models, have clipping and 0 attention to detail. TML has their own model, animation, rendering, paid voice actor, decent optimization, etc. In fact, I'd say the current approach of TML is probably the most unproductive way to earn money, by the time it takes to complete games like this, those who have the skills to makeit ended up finding a real job which pays 2x higher.
I know of 3 other good 3D adult action games but that's about it;
The Last Barbarian
https://f95zone.to/threads/the-last-barbarian-v0-9-19-1-viktor-black.14637/
Bioasshard Arena
https://f95zone.to/threads/bioasshard-arena-v0-5-328-versusx.11662/
Threshold Road
https://f95zone.to/threads/threshold-road-v0-55-public-absent-dogma.39705/
But yeah in relation to what everyone else is saying here, adult games take a lot of time and effort to make as you don't only have the non-adult elements to make you have the adult animations ON TOP of that. Then you have the story and levels and all the usual stuff that a normal game has. Personally I think we are lucky when quality adult games come along like Too Much Light.
A lot of these games are done by one person yet in scope and scale the good ones are as big as games done by studios with 10 to 100 people. It is pretty impressive and obviously takes longer to do.
We are seeing these games through their development iterations and if you take any popular game out there, Mass Effect, Witcher 3, Call of Duty 4, Team Fortress 2.... and you look at the iterations they went through during their 4+ year development you'd see that is just how development works. It is an iterative process where the dev tries stuff they think will be fun or good for the game only to later have better ideas (or worse ideas, it does happen as well).
Then on top of that good devs have to put up with a very negative community here on F95, the negativity has a cause though and it is that we as a community have been burnt far too many times by bad devs, and good devs have to put up with Patreon policy issues and restrictions and all sorts of other crap they may be facing in their personal life.
In relation to the funding of development, you can't compare this to indie games those people have a financial backing of some sort of say 100,000 USD to 500,000 USD to develop those projects. It pays their wages and living costs and everything so they can focus full-time on the indie game they are developing. While other projects the person has either built up savings or is in a situation they can work full-time on the game without income to then make profit after release.
That model doesn't work for adult games, most of these projects are solo devs who need to still pay rent and living costs and thus have a full or part time job and they thus need this extra income to make it worth the massive time investment making an adult game takes. For many their dream is to be able to do it full-time but that full-time salary needs to be provided by Patreon/subscribestar supporters and such. As most of these games are given for free.
Selling adult games is a very hard thing to do as you are very limited in options as to where you can even go about selling adult games. Steam allows games with adult content but will still ban games that it considers porn games and even on that they have absolutely 0 consistency.
As long as the game is good quality and we see consistent updates over the years I think we should just be happy with what we get, there are some really trash adult games out there and as JoeTermin said there aren't all that many good adult 3D games out there and even less so that ever see it through to completion state.