Hey, Sara,
The mesh parts are always an advantage as well as a disadvantage. It will let some of the sun get through, yes, but also it will allow air to go in easier, which is a good thing. I think that adjusting that, opening or closing depending on the sun's angle, plus, in the summer, a UV-protection in the form of a cream or spray, plus, if needed, a universal sun shade accessory can solve this if all else about the stroller fits your needs.
Also good to note is that most ultra-compacts have small or, in some cases, even almost non-covering canopies so I think this one is actually decent compared to most, especially the cheaper alternatives.