Climbing Ranked with Too Many Games Played

Is it truly possible to climb ranked when your account has hundreds to thousands of games played?

I see Youtubers and Twitch streamers doing "Iron to Challenger" marathons showing how 'easy' it is for them to climb out of low ranks to the high-end... yet the catch is their accounts are brand-spanking new! Their MMR is untouched and unblemished, let alone stained with TONS of games played in lower elos. But this gives off an impression that its just purely skill-based.

Problem is unless you want to sacrifice everything you've worked/paid for on the account... you can never get a fresh MMR. If you go on a win streak, it seems you are placed with those who are on a losing streak. MMR/LP gains are far lower than that of new accounts. You can be in one ELO and be matching lower ELOs even though you're doing well. Think of it as a baseball average - if a batter takes the plate for a thousand games vs ten games, the difference in his batting % over the course of time is drastic. The batter with a thousand games cannot budge his %, but the guy with ten games can inflate his % with one good game.

The penalizing a player due to them consistently using one account seems tragically unfair. It seems like you almost have to make a new account if you want any resemblance of a 'climb', like you see all over social media.

Maybe a solution to this? Some sort of hard reset option for accounts. Instead of creating a new account, why not offer a one-time only activation of a reset on your MMR? I dont know the specifics of ranking systems and its only a random suggestion I came up with...

But there has got to be something for those who have dedicated tons of hours to a game on the same account, have progressed over time and learned more and more - yet are treated as if they are as bad as their rank when they initially started.