Kydex holsters have lots of attributes - no argument there. They are inexpensive, durable, moisture proof, lightweight, available in many colors and configurations and seem to hold their shape for a long time. They are also quite popular these days and I am in no way trying to talk anyone out of one.
That said, I personally don't like them. As a pocket holster I can not imagine they would be comfortable for all day carry. I pocket carry about 1/2 the time and IMHO, the most comfortable, utilitarian, and wildly available pocket holster is a soft DeSantis Nemesis. For under $30 bucks it does everything better than any leather or Kydex holster made (IMO) - especially in the comfort department. Let's face it - if a pocket holster isn't comfortable it won't be used. The Nemesis has been in my pocket 50% of the time over the last 3 decades and they also last a long long time.
The reason I don't like Kydex as a OWB holster is not because of how it performs - no not at all. I am a traditionalist and like all natural products most of the time over "plastic". That is my own preference and my own hang-up if you will. So while I can not say too many bad things about Kydex holsters, they are not part of my equipment. The part about using a hard formed Kydex product as a pocket holster and not being as comfortable as a DeSantis Nemesis just makes so much sense to me. BTW, the Nemesis is also moisture resistant, extremely light weight, super comfortable, inexpensive and available in many different models for different guns.
Kydex makes a lot of sense as a duty holster for uniformed LE as it is inexpensive, works quite well, is durable with great retention characteristics and in a pinch can easily be replaced for a reasonable price if need be. I just don't see it as a viable pocket holster.