well, the RENESIS is the most powerful NA rotary engine ever sold by Mazda, and also the cleanest burning rotary ever, thanks to successful implementation of the side intake AND exhaust ports. It is also the highest-revving production rotary engine ever, thanks to much lighter and stronger rotors. Plus all sorts of minor yet very important updates to the rotary design, there is a reason why it won 2004 International Engine of the Year award, Mazda, all by itself, did a really good job bringing the next-gen rotary engine to the market.
there's really nothing 'wrong' with the RENESIS compared to previous gen rotaries, it's just that in the end, it's still a rotary, with all its quirks that typical piston-engine owners aren't familiar with...