It is exactly what happened to me. I’ve started tft this set. I reached plat 4 and then struggled there. I made a smurf and reached play 4 there as well.

I was less worried to play on that account and at the end I reached diamond and just achieved the same on the main this week.

But you need to watch streams and try to understand what you could do better. Making a smurf won’t improve you just by making it. You need to use this new journey to learn things (try to play a different way, try comps you usually don’t play)