Suarez still does some "classic 9" things quite good. He is annoying for defenders, can bind CBs to free up Messi a bit more and still scores a lot overall but that just isn't enough anymore.
He isn't fast and skilled enough to move around and do something different, passing him the ball under pressure often means the end of an attack etc and on top of him being slow he also either lacks the stamina or is too lazy to press the opponent these days.
On CL level this really shows. La liga isn't as intense and opponents are usually way worse so he can still score a lot because it's easier to create chances but vs the toughest opponents it isn't viable. I don't think it's a coincidence he is doing so bad in CL compared to la liga stat wise. A CF that scores some goals less but adds more to the team as a whole would be way better imo.
Idk who to bring in though. Ideally it's someone young and fast, that can score and create while doing his share defensively. So pretty much a perfect striker would be ideal who would have thought
Although i don't like Griezmann i almost start to think he would be a good fit, with another coach that can build a more flexible, mobile front 3. Not perfect but it's not like there are countless options for world class attackers.