How do I review someones code if they have more experience than me?

I’ve been professionally writing code for 2-3 years. Im pretty anal about code quality. I keep getting PRs from people with 10 years of experience that looks like it belongs on r/badcode. We are talking 100 line functions, massive commented out blocks of code, spelling mistakes, etc. It’s just really sloppy, and I feel like if this is allowed to continue overtime the company’s codebase will become messier and messier.

What should I do in this situation? I’m not very confrontational, and I generally don’t want to piss anyone off, especially not when they are 10 years my senior. If this were an intern, or someone with less experience than me I would be comfortable telling them what could be improved.

Should I just focus on the stuff I think is really bad? Should i only focus on finding bugs and put my concerns about code quality to the side? Any advice would be much appreciated.