Low starter is interruptible, overhead starter is slow and low-ranged, unblockable is jumpable and punishable, every character has overheads, Shazam has low start-ups too and his have half-screen of range, 50% no meter if you can manage to land it. Shazam can too, trait weapons have huge start-up and are interruptable. Ares can be beaten by the exact same things, the only difference is you can't punish or screw with Shazams teleport while most of the cast can Aug tech Ares on his wake-up.
Shazam has overheads, command grabs, and to my knowledge he has grabs that only hit standing opponents which means you have to be ducking to avoid them. That's not including the sheer amount of shenanigans and resettable damage, and his damage is solid enough for its cost on account of him gaining some decent meter.