Dynamics has had advanced find forever. Its not pretty, but it works. Its efficient, easy to configure, easy to find what you are looking for, and quick.
The NEW list building experience in marketing lists is TERRIBLE. Its slow, I have found 2 bugs in it, one of which prevented our team from using the list builder in the marketing list at all for over 2 months.
The current list builder needs the following:
Use less white space so I can use it on a small monitor or tablet
Make it fast to build a query
Make it actually return the data that is specified in the query
Reduce the number of clicks I need to build a query. don't ask me to add a row, expect me to want to.
make it easy for me to find related entities, fields on current entities with a logical sort
Its nice that the 'related entities' area separates the kind of relationship, but to most users (marketers, sales persons) the difference between a one to many and many to many is information they don't want or understand.

Really -- just update the existing advanced find to work in the UCI. Its not broken.