The best lenders return phone calls and emails. It really isn't all that hard to tell who will be responsive and who won't be. Just pick up the phone and call or send some email.
People who are slow to respond or who do not respond at all don't play well with others and we all have to work together.
When a buyer makes an offer on one of my listings one of the first things I do is contact the buyers lender. In a multiple offer situation if I can not reach the offer may go to the bottom of the pile.
My experience has been that if I can not reach the loan officer others like appraisers, underwriting departments and closers have the same problem which can delay a closing and that can be expensive and darned inconvenient.
So much of business is about responding to customers and clients and of course about there and being on time. Work with professionals who will be there for you when you need them.