Problem with the multitasking on iOS (iPadOS)

I have an iPhone on iOS 18.2 which has 4 GB of RAM and which works with the multitasking function much worse than my iPhone 5 on iOS 8.4.1 with 1 GB of RAM.

In 2018, after updating my iPhone 6s from iOS 11 to iOS 12, I noticed that the multitasking began to work much worse. Sometimes my iPhone couldn't even keep a second program in RAM, it just forcibly closed in the background while I was working with one program.

Surprisingly, my current iPhone with 4 GB of RAM (iPhone 6s has 2 GB of RAM) works no better.

It's terrible. I want to go back to 2014 and calmly use the iPhone and iOS, which are able to work normally with multitasking. Today my iPhone turned into an iPhone 2g, which didn't have a multitasking.

If the iPhone 5 with ios 8.4.1 supported all modern applications, I would rather use it than the new iPhones, because it totally sucks, to be honest. During my work with Telegram app and Google spreadsheets, I'm afraid to switch from application to application, because I have a constant anxiety about the fact that one of the applications will simply close in the background and I have to start all over there again. It's very annoying and unbearable.

Do something! The 12-year-old iPhone works much better in this than my iPhone, which is only three years old and has 4 times more RAM.