A company that I started in the early 2000s used cold calling to generate leads. It was very affective to generate solid qualified leads. We were lucky that we go an experience cold caller that trained other younger sales people. Having someone (either an agency or a person in-house) helping you is key to your success.

IMO, a good cold caller will work very hard to get to the right person, if that person exist. They will be committed and relentless to generating the lead for their sales team. They will work on their script to a point where they have answers for most types of questions. They will use the tools that they are provided (e.g. salesforce) to ensure to keep a log of what they've done and their todo list. And they will be in constant contact with the sales team to ensure that all information is provided back to them in a structured manner.

If you think that cold callers are waisting your time, simply try and tell them that you are not interested or point them to a different person who may be interested (if that person exists). There's no point for a caller to place a call to someone who has no interest in buying their offering, that's just a waste of time. Cold callers are "not" telemarketers.