Ballot Collection is and has been legal and secure in many states for eons. It is legit because of signature checking, ballot tracking, etc.
Fraud via ballot collection would entail a) forgery that isn't detected, b) ensuring someone requests a mailed ballot to their home then willingly gives it to a forger. Every election forgery IS detected and prosecuted, multiple ballots ARE detected and prosecuted too.
Security measures for absentee ballots, mail-in ballots, and ballots submitted via ballot collection are all the same. Further, there is no indication, evidence or proof that ballot collection, mail-in / absentee lend to more fraud, even in 2020.
Finally, since you keep talking about 2020, availability of more mail-in didn't drive voter turnout in 2020. A divisive, offensive candidate drove voter turnout.