That's because you're not thinking about Lightroom in the right way.
Although some people use it this way (and are severely limiting themselves), it was never originally intended as a one-stop workflow solution: from v1 the idea was to use it for your conversion and basic adjustments and then hand off further post-processing to PhotoShop or similar solution, pushing a lossless-format converted file to the pixel editor.
The fact that Lightroom's adjustment capabilities have been substantially increased over the years doesn't change the logic here: and you can do this right now, even if you decide to drop Lightroom - just export your files as full-sized 16 bit tiffs, or whatever other format you want to use, then you can do whatever you want with them in Photo, going forward.
Photo is analogous to PhotoShop, not Lightroom.
You "rent" pretty much any software, including Photo. All you're granted is permission to use it, and you no more "own" Photo than you do Lightroom, and if you want to stay current on an ongoing basis, you'll be giving money to Serif for the long haul, just as you would Adobe: