The opposite problem to a disconnect between strategy and work quality is when the agency team members constantly come up with ideas that they themselves can not execute.
Think "consultant." There are "problem pointer outers" and "problem solvers." Make sure you have the right ones. The reasons why consultants' ideas sound great, but when you try and implement them they sometimes fail, is that they are often disconnected from the actual construction process. There's intelligence in the idea, but no knowledge.
If the agency's ideas always seem to require the execution burden to be on your company, and if the agency's ideas require changes to your product, the way your site does business or how your internal product teams work, then what that demonstrates is that they really do not understand business outside of an agency.
If the agency has a diverse talent staff, those who have come from client-side in marketing, manufacturing, product development, or even completely outside of marketing, then their idea generation often understands many internal political constraints at companies.
It is the marketing group that hires agencies, not the product group, the research group, et cetera. Your agency should understand that.
The product group, manufacturing group -- whoever it might be -- has its own priorities for development. They do not usually involve you as much as you would like, and they certainly do not involve the advertising agency.
Note: It's fine if the agency gives you some ideas that they believe would help your business that you can pass on without causing internal ire.
But if the agency's programs constantly require internal juggling acts in your own company to accomplish, then either your product is not that good, which is possible, or the agency does not understand client businesses well enough to deserve yours-- the more likely option.
Great ideas are executable.