I guess the chess.com tactic trainer is focused on finding those tactics/patterns quickly and thus forcing your brain to think quickly.
I'm also a fan of no time limit on puzzles and alternate correct solutions:
I think you'd be a fan of www.ideachess.com in this regard,
Best.
sometimes I enjoy going thru my free 3 exercises daily.
Issues -- 1) Alternate successful solutions are not given credit. If I would be concerned about my Tactics Rating, I would send them to Admin, but who cares.
2) At times I may take a minute longer than their average solve time. Though the software tells me my solution is correct for all moves, I have sometimes lost up to 7 points ! How is that determined ?