Unfortunately not. The problem is not caused by the number of theme and color scheme files, but the number of Theme Options each of the themes provides.
Each entity which is created, requires memory and needs to be handled by the theme engine, no matter whether the associated setting is true or false. This fact can easily proved by the RAM usage of ST. If a (let me kindly name it) "normal" theme is active, an empty ST window without documents, requires about 30MB of RAM on my Windows box. As soon as I apply either Material Theme or Boxy Theme, the RAM usage increases to about 60..90MB!!! (2x to 3x more!!!)
If you open many windows and maybe documents those themes can quickly cause much more RAM to be consumed and the GUI becomes noticeable slower even on 2k displays over the time. With a 4k display things might get even worse for sure.
What you do with the tons of Theme Options, was IMO never meant to be done with them.
Things would get much better if you'd split the few themes in many and heavily reduce the number of Theme Options per file.