CVT maintenance question

I have a 2018 crosstrek with 152K miles. Recently, during a long road trip, I had the experience of the CVT shuddering and or malfunctioning at medium throttle levels. Basically when I’m trying to accelerate at 1.5K to 3K RPM or so. It happens now every time I drive but only after the car warms up. There is also a faint burning smell from under the hood. If I am aggressive with the accelerator and push it well above 3K rpm and then gradually back off, it will drive in the 1.5 to 3 range, but then will shudder again if I try to accelerate. In short, I need to either barely touch the accelerator, or floor it, to avoid this problem.

I took the car into a shop today in hopes of checking to see if I could add or replace the CVT fluid if perhaps it’s wearing out as the car is aging. The guy says that it won’t really accomplish anything to do that.

I’d appreciate thoughts from anyone more knowledgeable than me about this, as I’m not sure what to do.