They gave you a slap on the wrist. You were harassing your teammates. Be happy it wasn't a temp ban. They're giving you a chance to reform your behavior.
The other people may have gotten disciplinary measures as well if they mirrored the toxic behavior you exhibited. However, as a privacy policy, Riot will not disclose anything about other players disciplinary measures to others.
Some examples of why you have your chat restriction:
omnicron007: stfu
omnicron007: or ill feed youe lane
omnicron007: im better than you
omnicron007: u suck lol
omnicron007: im stealing your farm
omnicron007: im taking all your farm cait
omnicron007: watcha gonna do
(you're insulting and harassing your teammate)
omnicron007: u suck
omnicron007: and your duo
(harassing them again)
omnicron007: youre just feeding now lol
omnicron007: caitlyns raging for no reason lol gg
omnicron007: and her duo
omnicron007: i really dont know why youre so upset lol
omnicron007: maybe you should focus on improving your gameplay
omnicron007: our adc does no dmg
omnicron007: we cant win
(You're harassing them again. Your "maybe you should focus on improving your gameplay" isn't constructive criticism. You're just insulting them)
omnicron007: hes been complainign since champ select
omnicron007: its ok the 2/9 caitlyn will carry
omnicron007: ?
omnicron007: im better than you
omnicron007: youre 2/9
omnicron007: literally the reason we lost lol
omnicron007: its ok though i dont mind. just play better next time
omnicron007: for your teams sake
(Same as the above. You're blaming the cait for losing the game and your "its ok though i dont mind. just play better next time" isn't constructive either. You're just insulting them and trying to seem like you're being nice but you're not.)