Any advice gratefully received please.

I have been selling on Amazon FBA since 2017. At one point I was turning over £1000+ per day. About 3 years ago my sales started dropping and now im Lucky if i do £100 a day . I have created new listings with new products, and these have sold a little bit. People tell me that Amazon’s algorithm has changed massively in the past few years and it could be that all my older listings are obsolete. Does anyone have any advice?/ experience with this?