Daymond John says Playboy is making its best move in years by joining forces with Cardi B ... because she'll bring her legion of young fans to the iconic brand, while also making much-needed changes to it.

The "Shark Tank" star joined us Friday on "TMZ Live" and we got his reaction to Cardi coming onboard with Playboy as its first-ever creative director in residence.

Daymond says the move makes sense for Playboy on several levels as they move away from traditional print magazine and focus in on a digital rebirth -- he envisions Cardi breathing life back into a brand with a following that skews much older.

Cardi says her new role with Playboy is a "dream come true" ... and Daymond tells us why he wants to see more of those dreams becoming a reality before deciding if Playboy is a worthy investment.

Daymond's hoping Cardi will be more than just a figurehead ... and he's interested in her introduction of sexual wellness to a brand formerly known for naked centerfolds.