Clearly they have effects. Heck insulin is a peptide. And pretty sure it has a benefit for those with diabetes. Dismissing peptides outright is just as silly as thinking peptides are the solution to everything
Anyone talking about "taking peptides" as a meaningful sentence is absolutely dismissible in the same way someone talking about "taking chemicals" is dismissible.
Injecting poorly-studied grey market peptides seems like a bad idea.
1) PT-141 is a peptide that releases sex hormone into the blood and literally makes you horny, and its primary use is for premenopausal women that have low sex drive.
2) PNC-27 is a peptide that supposedly attaches to the cell membrane of tumor cells and performs cell lysis (death) of the tumor cell, and it's supposedly affects many different kinds of tumor cells: breast, pancreatic, lung, colon, ovarian, cervical, and leukemia
3) Epithalon is a peptide that is noted for extending telomers on chromosomes, leading to longevity benefits.
4) MOTS-c is it peptide that in animal studies is shown to boost physical endurance and mimic molecular changes associated with training/exercise.
Telomeres are part of your anti-cancer mechanisms (they stop cell reproduction after say 60 DNA self-copies to help fight unbounded cancerous growth).
If chasing 'benefits', you'd want to be careful before fucking with that mechanism.