Why shouldn't you rely on tier lists and build all the S tier characters?
If you don't know when, where, how, and why units are used, there's no point building them!
Units that synergize with your existing roster are better than an "S rank" unit who plays alone.
Many tier lists fail to provide a reason for their ranks; This can hide biases or misconceptions of the author.
This is especially true for PVP tier lists. Personal experiences