Support is matter to rank up

I've seen a lot of mmr gain post or tip to rank up say role does not matter at all .
But why always smurf or booster just pick pos 1/2 .
Like morph ,meepo, clinkz and invoker something ?
They rarely pick 4/5 in 10 game.
So, is it possible for low-rank 4/5 player to rank up ?
You will say we can climb slowly but how long it take 1k to 6k , may be 2-3 year ?
Should we change pos 4/5 to 1/2 ?
Low-rank support always feel like toss a coin which carry they will get.
If you are immortal player, will you pick support 10 games in a roll for smurf account?
Some youtube content show how support effect the winning game but they always get decent carry.
In sea server you need to learn 5 language for communicate,get they always right carry and rizpol build mid.
Even you play well , support can't do shit like true core .
You pull , you stack , you ward , you save them, you push and then they die without BB and game end .
GG support life .
sry for my english.