in the mainstream

in the mainstream (of sth) (accepted by most people, conventional)

go mainstream (of sth) (to spread all over) — стать обычным делом; повсеместно или широко распространиться

Example: Tattoos go mainstream. Young people are going under needle in large numbers, especially women. — Татуировки стали обычным делом. Молодежь идет под иглу в больших количествах, особенно девушки.

See also
[keep up with the Joneses]
[follow the crowd]

outside the mainstream

Example: His views place him outside the mainstream of British society. (MM)