The endless scroll.
Also shit 'news' sites that are nothing more than a ruse to force you to watch adverts.
Dual income mortgages. It hasn't done us any favours to count both partners salary when assessing the amount lent. If they'd just stuck at basing lending on one salary, whichever is highest, it would have reduced house price inflation, also made it easier for people to buy on their own as they're not disadvantaged so much compared with dual income households and also built in resilience against job loss, illness, childcare costs etc.