thw major point is that he uses his own max range by himself. none of units can do like that w/ penalties.
ps. tbh puma's low penetration doesnt be a problem much. BECAUSE he fight agaisnt low armored allies tank (except the heavy tank)
the Puma is great against light tank but its penetration is mediocre against even the mediums. The puma have 80-100 penetration at 50-35, and even that is weak against the 150-160 on the allied medium. The puma also only have ~55% accuracy at long range and the regular 50% moving penalty. It would shot its shot regularly.
If you can't micro the Puma well enough, it
will die in the late game. it have very little armor to speak and not that much HP at 400. The range of 50 puts it under the 60m of opposing TD well offering a scant 10 safety buffer against medium. The puma will lose against most medium in a slug fight.
The Puma is also poor against infantry, it probably have the worst anti-infantry power among the light tanks (AEC is probably a bit better). It can't shock at all so its sole use is to counter enemy vehicle. It is an extremely defensive unit designed as the anti-shock unit.
By comparison both the Stuart and t-70 are much better than killing infantry.
The jackson got a sight nerf because it got a hp buff to 640. I do think the jackson should have been buff to be similar to the puma and the Unit is a mess atm.