If issues are being opened faster than they are closed, the number of open issues is going to grow without bound. That's just basic queuing theory.

It's also the case that the average age of open issues will grow without bound. (As the number of open issues grows, eventually you get to a point where more issues are untouched in any given period than are either opened or closed.)

So, it's very easy to get into the state where there are lots of stagnant issues. It's going to happen automatically unless you do something to fix it. Something needs to happen so that either fewer issues are opened or more issues are closed.