The point of removing tech rating was never to make entertainment rating the sole measure of rating TASes. TASes can have merits other than being entertaining, and ratings should be able to reflect that as well. For example, I would rate
[4567] NES Super Mario Bros. 3 "game end glitch" by OnehundredthCoin in 00:00.22 low in entertainment rating due to lack of entertaining gameplay, but on the whole, it is a high-quality and notable achievement, so I would give it a higher overall rating. Not doing so would be like giving Citizen Kane a low score on IMDB because it isn't a comedy.
So ultimately, having a singular rating system isn't really compatible with either the notions of entertainment or technical rating, so we can't provide compatibility for either. What we did do, was to have compatibility (as much as was possible) with the overall ratings for TASes as they existed previously. It's unfortunate that this ruined your system of entertainment rating, but entertainment ratings themselves technically now also don't exist anymore, so it is what it is.