There is really no point upgrading belts most of the time.

If I spend the currency to upgrade a belt it gives me little overall power. The belts in POE 1 were better. All of the belts I drop start with stats related to flask charges and every type is the same. There is no clear differentiating factor.

I would recommend going back to the POE 1 belts that all had something different to offer and have their base stats increase or integrate the belt into the armour set and give them armor stats according to one of the six armour types. Alternatively yo ucould go the route yo udo with jewelry and have them all hit a specific stat like life, str, dex, int and so on.

For example I just got a quest reward of a belt that is 10 levels above my old belt but empirically my old belt is far better. I would post the screenshot if this forum allowed it.