Employment is one of the most obvious, salient examples of market failure I can think of. Exploitative employers engineer situations where employees can't even use the job market, because they need a job and job-shopping (e.g. taking time off-call to do interviews) will lose them their job. Example: Arise Virtual Solutions[0].
If that's not a good enough example? See the gig economy. Companies taking over a service sector “with an app”, at a loss (using investor money), then squeezing the money back out of employees (e.g. by misclassifying them, not telling them how much each gig pays, programming virtual micromanagers to work them to the point of health problems in the name of “efficiency”). To use your words:
> If you are talking about welfare of specific group of people (at the expense of others) then you are right.
Who's “we”? I was under the impression that https://en.wikipedia.org/wiki/Market_failure was accurate.