Yes, so far Apple seems to leave hearing issue mitigation to 3rd parties. But hearing issues are widespread, if not always severe enough to merit specialized equipment. There’s a lot that could be done beyond just adjusting R/L balance or setting sound to Mono or whatever Headphone Accommodations is capable of, Conversation Boost etc.
But as far as specialized equipment, there are a bewildering number of MFi hearing devices:
https://support.apple.com/en-us/HT210386