i don't remember now and it seems impossible to find an article with my list of complaints but:

1. feature parity wasn't there. i already have whatsapp,you're asking me to move. feature parity would be minimum requirement

2. it didn't auto discover people like whatsapp does(or atleast it didn't when i tried it initially), people needed to sign up for it adding friction to an already unpleasant process of getting people to switch

3. duo wasn't in allo and allo wasn't in duo. if there had been just one app it would have had a greater value prop(at the time) of chats with video chatting. instead there was a whole 'nother app to manage. once whatsapp announced voice calls(followed by video) getting anyone to "allo/duo" was absurd

4.i remember number porting was buggy in some way, just flat out didn't work for 2 days

can't remember the rest but i remember something about the emojis bugging me(google implementation different from whatsapp) and being unable to send pdfs

it needed to compete from day one not "find it's feet" gradually. i find this to be a problem with all google products really