Both major flagship lines refreshed in the last month, which produces the annual question. The honest answer depends almost entirely on the age of what you hold now.
If your phone is one year old
No. The generational difference is small and almost entirely invisible in daily use. You will notice the camera in specific conditions and nothing else.
If it is two to three years old
Probably not for performance, which is adequate. Possibly for the battery, and that is worth separating – a battery replacement costs a fraction of a new phone and restores both endurance and, on some models, speed that was being throttled.
Do that first and reassess.
If it is four years or older
Now the case is real. Software support may have ended, which is a security issue rather than a feature one. Camera improvements over four generations are genuinely large. Battery is likely well degraded.
The reasons that are actually good
Security updates ending. This is the strongest single argument, and it is the one least discussed.
Storage permanently full, which cannot be fixed on most phones.
A camera that matters to you, if you photograph a lot.
Something broken where repair costs a meaningful fraction of a replacement.
The reasons that are not
A faster chip, which you will not perceive. A slightly better screen. Being a year behind.
The cheaper path
Replace the battery. Buy last year’s flagship, which drops sharply in price once the new one lands and differs very little. Or buy refurbished, where the discount is large and the warranty is often reasonable.