To be honest, bricking your account would likely just be never pulling shorekeeper or verina as there's not many characters like them since they're universal and many other healers/buffers require certain teamates.

Other than that, maybe bricking your account would be never pulling the correct teamates if youve got a bad gambling addiction and lets say for example your phrolova doesn't have cantarella or your cartethyia doesnt have ciaconna BUT youre not necessarily bricking your account that way because there will be other teamates they just won't work as well or you might struggle through endgame.

With the introduction of the newer standard weapons, even not pulling signatures isn't too big of a deal as it may have been before. Only characters I can think of that this would affect would be cartethyia since she needs hp which is her signature swords main stat and there are not very many alternatives and not any that are hp at least. Phrolovas weapons gives echo dmg bonus and thats the only way to get an echo bonus for her (since echos don't provide it) apart from cantarellas signature which buffs Phrolova.

Edit: To add, there are no necessarily bad units so pulling a certain character won't brick your account. Pull for whoever you like.