Puzzle Theme Variety

As an average to low-rated player, I have noticed that while the ease of doing puzzles has changed recently (I currently do Regular difficulty puzzles) I have also noticed the increased variety of puzzle themes I'm finally being exposed to during a puzzle session. As a long time puzzle solver, (my current account has been open since 2021, my previous account was open from 2010-2021 and manually closed for personal reasons before opening my current account per policy) the curation of puzzles did not give a variety of themes. 
Since whatever alleged change being implemented I am now being exposed to to a higher variety of puzzle themes. Majority of themes were at zero percent not due to failing puzzles in those themes but they were not present at all in the puzzles I was solving. To practice themes I would need to select custom puzzles and then the specific themes for the needed rating range and practice these puzzles unrated.
From my understanding, you can change your puzzle difficulty in your settings from Regular to Hard to Extra hard. Someone somewhere mentioned a slider. The custom puzzle has a range slider (or did) now you can enter the rating range in manually however custom puzzles are unrated. I have not noticed any changes with this.
Some change is good. I am being exposed to a variety of available puzzle themes on my level. It makes me feel good to finally be given a curation of manageable puzzles that have provided a variety of themes to practice and have my rating increase - rating however shouldn't be the focus imho but that's a conversation for a different thread) however I'm sure whatever is happening on the backend once resolved, all the ratings will most likely once again be adjusted (as has happened during various other odd and regular updates over the years).Showing a partial of the themes that were once zero percent because I was not getting any puzzles in those theme sets.