Well, by definition. If they're not observable in SOME fashion, surely we can't know they're there or count them?

We can predict how many galaxies there should be based on physics. Anyway, my point was more that if we assume the universe is infinitely large and roughly uniform in density that it should have *infinite* galaxies in every direction

... but most are outside of the observable universe, because light speed and cosmic inflation

And unless something drastic changes, the horizon of observability is closing in on us, such that eventually our galaxy will be all that is knowable to its citizens, if any survive that long. In other words, there may be 50,000 galaxies in that circle *today,* but over time, that number's going to be fewer and fewer (for all practical purposes).

And if they aren't observable then arguably they no longer even exist from our perspective.

The universe is flat. If you can't observe a galaxy, it's gone and fallen off the edge of the universe.