Is the 2021 Toyota Corolla air conditioning system reliable?

The CVT you’re referring to is actually the car’s transmission rather than its engine. And since the engine is what drives the air-conditioning compressor, it’s the engine’s power and torque that determines whether the car still drives nicely with the air-conditioning switched on, not whether the transmission is a CVT or any other type.

But I think I know what you are referring to. And that is how well the car’s engine and its CVT transmission are matched. Sometimes, a transmission can gobble up a fair bit of horsepower and torque and that can take the edge off performance. Throw the switch on the air-conditioning and there’s even more load on the engine, making it feel even less perky. In that sense, I think the Corolla as the newer design would have a more efficient transmission and that could mean that it feels the load less than the older Honda might and, therefore, holds on to more of its original performance.

But the second thing you mentioned, that your car’s air-con doesn’t really keep up at temperatures over 30 degrees is more likely to be a problem with the air-con itself. You might find that a five-year-old car (such as your Honda is) is ready for the air-conditioning system to be serviced and perhaps even re-gassed, which might just return it to better health. For the record, Toyota’s have always had some of the best-performing air-conditioning systems in the business over the years, and I very much doubt that a 30-degree day would tax the air-con in a new Corolla one iota.