Shield is pretty potent slow. His entire kit is best suited for him to protect an ally and peel enemies from them. That's his big strength. Daisy, his golem at max rank does decent damage (about 200 per hit) and the knockup from her is a line AoE, meaning that it can hit pretty hard in a teamfight.
Ultimately, he doesn't excel in a standard game and his team needs to be built to utilize his kit. For example his Q gives a good initate to a tank, but if he's the tank, there's something wrong, though he would be building on the tankier side.
Bonus Buffs in higher tier play make all the difference for them, so that's a thing.
If you play him correctly, his DPS is loaded into his on-hit, through extended fighting. And if you really look at the range on his bushes, they can do a few things. One is scouting, since they give vision when placed and the other would be blocking line of sight from your opponent. (Especially good using it on the Dragon to hide it while your jungler wipes it.) Plenty of various interactions are really the key to making him play best, but again, not the greatest without the right team.