Not being able to steamroll whole factions early game with no support is hardly same as becoming piece of shit.
And its not supposed to perform better in late game(although its THE very best and cheapest light vehicle with THE very best scaling in game thanks to being immune to 2nd ATG shot being a kill shot at vet) , its T34 of light vehicles, mobile, cheap, fights both infantry and armor, effective in numbers, but outclassed by more expensive stuff.
It is the the light vehicle with becomes so fast obsolet that quick. 251 can still be used as refresh or flamer. Same for M5+good AA ability (better than 222) and inf-suppression. T70 can capture points and also in late-game its gun really works good because german-inf don't get AT that that mass (Long ago I used Schreck or saw them on PnzGrens). AEC can still pen mediums and support.
222 only is good with Vet2 with sigh-bonus. Or with Scope. But it is a main-line unit in my opinion. A must-have (Ostheer is kind of build around it in my opinion, like StuG G) it should get some boost in lategame.
I am for a bloob-counter like Centaure (like 6 shots of 251-FlaK for little aoe buff) or a pen-buff on time. Replacing the infantry-scan.