Your rude comments certainly make me wonder why you're so unhappy with your life that you constantly feel the need to bring people down on SDN. There's no need to discredit other people's accomplishments just because you don't agree with where they got an LOR from. When your university has ~50,000 students and your bio or chem classes have 200-500 kids, it is challenging to get to know your professors well and adcom knows that. With good stats and ECs, a LOR from a TA who actually knows you is fine. The point of these letters is for someone to vouch for your character, not make up bs based off of your resume. I was accepted to 2 great schools and I'm sure adcom didn't look at my letter and value it any less. The only person who is bothered here is you, so please keep your unnecessary and unhelpful opinions to yourself.