QA teams are not meant to delay the product release but its otherway

I am in software testing/QA industry for over 3.5 years and have seen different kind of people in this industry. Many times I have seen that QA feels happy when they delay the product release by finding a high-priority bug just before the release. But is the product release delay not bad? Well it may not be as bad as a low quality product but it is. If QA finds a critical bug (which exists in all prior builds) just before release than its as responsible as the dev team for delay in product release.
Frankly speaking, its more of QA responsibility to release the product on time. QA can ensure the same by getting involved very early in product life cycle. By involving I don't mean creating the testing documents, but about white-box or code-review kind of testing, which helps in finding bugs very early in product life cycle.