Wait until you've seen the Captain Marvel film! You don't know what she can do yet.I find SW being the "most powerful MCU character ever" far more believable than Captain Marvel.
Vision was completely useless in Infinity War though. Especially after zapping everything in his path in Ultron and lifting Thor's hammer.
I asked the same thing earlier in the year and Night Prowler came up with an an explanation.Thor's quest for Stormbreaker didn't make a lot of sense, didn't he learn to use his powers without a weapon in Ragnarok?