My other Samsung device are s9 and A52. Shouldn't the s22+ charge at the same speed as the older phone since battery capacity is similar?
I don't understand the discrepancies between older phone able to charge faster than new phone as it should be backward compatible.
Nope. You have to understand. S9 was the last series to do 18w fast charging via A to C standards. A52S is only 15w.
And those 2 phones are on older charging technology. Different protocol to begin with also. It follows the Quick Charge 2.0 protocol in those era.
From s10 onwards it was all newer protocol called PD PPS 25w or 45w. They have moved on.
Quick Charge 2.0 is not the same as PD PPS. However in the phones battery menu, you could turn on the fast charging option to fallback to Quick Charge 2.0. But that will still be slow at 18w.
In order to maximise the charging speed. You will need to change the charger to a PD PPS charger. Go take a look at s22 accessories thread. I have posted numerous compatible charger there.