Am I just being a brainlet or does there being different sized infinties not make any sense?

Yes I understand the concept of countable and uncountable infinities and how theres an infinite amount of decimals that come between 0 and 1, but even if you start off with a decimal with an infinite amount of 0's with a 1 at the end and count up from there its not like we're going to run out of numbers, theoretically the countable infinity would keep up with the uncountable infinity from 0 to 1 and beyond. Thus theres no real difference in the size of the inifinities.