It depends on what you mean. If you're ripping the videos, then uploading them under your own account, and embedding, yeah, it is copyright infringement.
However, if you're just using the embed code that YouTube and nearly every other video platform offers, then no. You can still monetize the site, just not the video itself.
Here's a scenario. Let's say I have a site that teaches people the basics of wordpress, but during one of my articles, I don't feel like making a long video that demonstrates how to make a sticky menu in Genesis. So I'll just find someone else who has already done it, and embed their video in the article. I still have affiliate links for themes, hosting, etc in the article, but just not the video. This is 100% legal.
Now, if I find that same video, rip it, blur the watermark, upload it to my server or YT channel, and then embed it, it is going to get a DMCA letter. Just make your own stuff OP, if you're thinking about going that direction...then you can sleep at night, plus you are building a channel.