I think Google used to be "cool", but it is more prestige now. There is definitely still cool areas which Google works on(AI, self-driving), but overall, if you are working on Gmail, there is nothing cool about it and the main motivation is not to make Gmail more awesome, but to get paid and beef your resume for future work opportunities.

Unicorns vary, but mostly they are B2B enterprise companies, which do very boring stuff day to day. But something like Discord will be exciting for many people to work at.