Is it correct to say that a person "has been joined the team"? Is "the user has joined the team" still correct? This sentence is used as notification on the website.
The user has joined the team.
is the normal form.
The user has been joined to the team.
is grammatical but unusual. "Be joined to" usually means "caused to be physically attached to" and would not be used for the metaphorical sense of joining a team.
But I can imagine somebody using "join" in a non-standard transitive (causitive) way, meaning "cause to be come a member", just as people sometimes use "volunteer" in a similar way ("He volunteered me to do the work").
So I can make sense of "The user has been joined to the team" in that way - somebody has made the user join the team; but it is not a standard use of the word.
Without "to" it is not grammatical.