There are so many devices that support mp3. My 15 year old car plays CDs with hundreds of mp3s with zero issues. I still have somewhere a mobile CD mp3 player that will work with both new files and those I harvested 20 years ago.

There is surprisingly still some mp3 releases online, including content for kids which for me was mp3 only so far.

I have a lot of FLACs but with years it makes more and more sense to me to keep it unified.