Somehow this sort of thing never happened to a recent device like the S7 back in the days of CM, before it became Cyanogen Inc. Between the death of Cyanogen Inc. and the birth of LOS a crucial ingredient appears to have been lost, leaving the project as a whole less vital that it was before.

Overall interest in the ROM and android modding community has been decreasing. CM appeared right when android really started gaining traction and the modding community prospered. That was when phones were seen as the cool new tech with all these interesting features. Nowadays most people don't care what is in their phones as long as it runs the apps they want, takes decent pictures, and lasts for a decent part of the day. It also doesn't help that nowadays app developers have started intentionally crippling apps when a custom ROM is detected.

Because of this most people don't contribute to android ROM projects anymore. For a lot of people it just isn't worth the effort those that do care tend to keep up with new tech and buy the latest and greatest tech so they aren't maintaining old devices as much anymore unless they were major hits or a personal preference of the maintainer.

As for why a lot of features have disappeared, through the whole process of surviving the Cyanogen Inc. issues, it took everything the community had to keep basic android supported let alone all the extra features considering how many devices they support. Now that Treble has been deployed, this shouldn't be so much of an issue but maintaining so many old devices that have long been deprecated isn't easy.

Also, as for why the S7 is no longer maintained, apparently there was some bs issue with the software license on the S7 binaries.

The secret ingredient is cash.