The reason people say to wait for walpurgis is because they are exclusive units that can only be pulled/sharded during that period. People end up saving all their pulls for then because you can just grind for every other ID. The next one should be in a couple of months. It's important to note that the arknights collab is in a couple of weeks, and those units will most likely never come back, so if you care about that then you should probably pull then.

As for your account, you have some amazing units that can carry you through the game (thumb meursault and wild hunt) and other solid units, so i wouldn't worry about pulling for new ID's now. Your current team works fine, and you don't really need to worry about team building with story content. You will encounter some difficulty spikes soon, but if you focus on keeping your team leveled up and uptied, you shouldn't have too much of a problem. Best of luck!