Your phone is low budget/tier, which is fine, you get what you get, but you need to have realistic expectations when it comes to optimisation of a niche/budget brand with a heavily customised Android-based OS.
That 8GB RAM is a marketing gimmick because the CPU and GPU are massive bottlenecks. It’s never going to actually push 120Hz in FCM, even on a basic 720p screen you got. The hardware just isn't there.
To compare, my old 6 YO Samsung S20Ultra that I use for MM autoplay, is still twice as fast, a phone that I bought in 2020, so yeah...