Why do most Theravada monks teach Buddhism in a very nihilistic way?

I feel as if they teach the Dharma in a very nihilistic way and that makes my OCD worse. Probably that's the nature of Theravada but I wonder why? I recovered from severe religious OCD four years ago after listening to Thich Nhat Hanh when I was tormented by sermons by Theravada monks (Sri Lankan). I don't wish to bring any hate to any Buddhist tradition, this is only an observation. Also, this is my perspective at the moment, I can be wrong.

Edit for those who asked me to be more particular : I guess it's the way how some monks describe the impermanace of the body and life in great detail. It's obviously a fact but listening to it makes me feel guilty for enjoying harmless pleasures in life (Like reading or watching a slice of life film, going on a trip or a hike) I guess some monks even put emphasis on renunciation a lot. I went to a monastery two months ago where a monk questioned why we didn't want to renunciate. It actually lead to a relapse of Buddhist scrupulosity. The monk's intention was to convince us that our lives (even as lay Buddhists) will not be helpful in eagerly following the path. His intention was probably wholesome but it just made me feel really guilty. I just wish he explained us how we can follow the eight fold path as lay Buddhists instead of questioning the simple pleasures we enjoy in our lay lives. Maybe on how we can practice detachment as lay Buddhists. I remember wishing for the sermon and the questioning to end the entire 30 minutes.

I really wish I could renunciate at some point (it's actually easier follow the path that way) but I'm not ready for it now. I'm still 19 and I still enjoy harmless pleasures and I still have attachments to family/friends.

I really wish I could renunciate but my mind is not ready for it so I feel guilty about it. That's created by OCD too I guess.