One thing that really makes my skin crawl, is when I tune in on a tuesday and wednesday to watch champions league footy (preferbly with a pint on my hand, a remote in the other, and a skillful technically masterful EPL side playing in the game) and then I see such horrible pitches. Teams that have no business hosting a champions league match. teams with horrible pitches. You know what teams I am talking about. those random ones. It makes the game so unbearable to watch, the ball bobbling around all over the place, and teams like Barcelona suffer because of other teams not being able to muster up a decent pitch? I understand not all teams can have 5 star stadiums but at the very least maintain your pitch properly. Its one reason why EPL is so amazing (along with the superior speed skill and intelligence of the game there), more good quality pitches.
Any examples you can point out in particular? I can only watch the matches they show on Fox Sports 1 & 2 and so I'm only able to see the matches with the big names. My guess is that the examples would mostly be in Eastern Europe and Russia where large stadiums are used quite heavily and the climate isn't terribly conducive to growing the well manicured pitch you see in the EPL with England's climate. Would you be ok with a switch to field turf?
Reading the CL and EL regulations, it seems like Uefa makes teams go through a hundred hoops to get artificial surfaces in play. As P'Jay points out, this is do-able for the big western-European countries, but not the smaller, eastern countries. (You can switch between natural and artificial once? At the end of the group stage?)
A bad pitch also increases the risk of injuries. But I don't think your (---Z---) complaint can realistically be regulated by UEFA, there are too much variables in question, club financial policies - which they have the right to control, regional climate, structure of the seasons/off seasons in different leagues, the hiring of the stadium for uses of other sports, the inconsistent frequency of participation in European competitions by those smaller European clubs, etc.