My guess is that US surveillance and intelligence agencies operate like many other large government beaurocracies: with high levels of administrative incompetence, mismanagement of resources, unscrupulous decisions in the service of individual risk -avoidance/status-seeking, etc.
I suspect Snowden does them a service by making us all feel like we're under a big, scary, watchful eye.
In actuality, they probably do collect unholy amounts of data, perhaps even illegally... But they probably don't know how to process it effectively and if they do, they probably struggle to turn those insights into action.
It's easy for them to collect Facebook friends and Google searches, not Signal messages and DuckDuckGo queries made in an incognito window. It's easy because they can demand tech companies "hand it over" without actually hiring and assigning the skilled and creative people they'd need to figure out how to overcome the modest obstacles privacy-conscious people erect.
If you're a decision maker in one of these orgs, you'll be recognized and praised for cheaply trawling for privacy illiterate pedophiles and easy-to-identify, state-affiliated Twitter bots.
OTOH, you might not get promoted for spending hundreds of millions of dollars breaking into end-to-end encrypted convos only to find out that 99.95% of the data is benign and the .05% that's substantively suspicious requires a warrant and an FBI surveillance team to gather enough evidence to actually go to trial.
tl;dr: cheap measures to protect your privacy probably go much further than you'd think, because while they can be overcome individually, they're not worth overcoming at scale.