Is it just me or do those "cold brew at home" kits suck?

Simonfletcher thought this was worth mentioning said
2

Bought one of those “make cold brew in your fridge overnight” setups. Followed the instructions, even used decent beans. Tasted like bean water mixed with sadness.

Do any of these things actually work? Or is it all just marketing for people who don’t want to shake a French press?