I honestly don't think much about it and everyone should be free to play the game however they prefer. Pp-maps have been a thing ever since the system got implemented, whether someone wants to make use of such maps to increase their rank with comparibly less effort is up to each person themself.
It's not like people are cheating the system, it's a part of the game and as long as anyone can fairly make use of it, then I think nobody should be judged or blamed for farming. The majority of people that complain about pp farmers are usually the ones that lack the skill to properly farm themself, so they prefer to swing their morale cudgel on others instead :p
Although I do agree that the system is a bit flawed and reuqires some work to make difficulties of all skill sets equally rewarding.
If ranking and pp are things you care about for your self-confidence and give you a feeling of fulfillment/enjoyment, then why not? It's a game after all. Simply focus on your own game, and not on others. For a lot of people pushing ranks is like reaching milestones, and that's where fun and motivation lays^-^