the primary firehas an extremely slow damage rate in the LV. 1, but this is not the main problem, but rather the fact that it does not have many opportunities to highlight its most interesting peculiarity: reload the ammo through the shields.
it could recharge them against winston, orisa, reinhardt and brigitte (the latter is more difficult due to bash), but there are very few opportunities to do it. something smarter would be to create real specific advantages to certain characters: to load the weapon even when it hits the shield HP and temporary enemy barriers.
it would create an advantageous response against characters who use temporary barriers (ultimate of lucio, Doomfist and Hammond barriers) and if torb has a ultimate specifically designed against the HP armor and against Brigitte, I do not see why Symmetra should be limited only to the shields in the field and not to the HP shields (Zenyatta, Zarya and Symmetra)