Is testing merely a Bug filtering process?

In an organization engaged in software development, usually each software goes through testing process by a separate set of team in the organization know as Testers meant exclusively for the purpose of testing. It matters most what this process is being thought as by the development team, project leads and the management (and also the customer). Testers are taken for granted as Bug Filters and testing as bug filtering process. If that is so, the management is at mistake, more so, if testers or QC department also thinks the same. This sort of culture is good for testing purposes, but is not so for the purpose of improvisation in the development process. Testers are safe as they are able to dig out a good amount of bugs every time. Bug removal time is substantial. Even the targets of product hand over to customer are met.

Isn’t the testing team’s result decrease every time even after increased efforts! That means the development team in maturing with each round of testing and development. This can happen only in case testing is not merely thought as the bug filtering process.