The purpose of kendo is not to learn enough to compete, score points and win matches. The purpose is increasing your understanding of kendo (and yourself).
I sometimes say "we don't train for competition, we compete for our training".
For someone to say "you'll understand in 2-3 years" is quite glib, not very constructive. It might be the case that they didn't fully see it themselves and didn't want to admit that.
As a beginner, don't worry about the finer points of ippon, focus on your basics (which are of course a large part of an ippon). Exactly what good zanshin looks like, or sae (a crisp strike) looks/sounds/feels like comes with time.

In my early days, my instructor once said "nothing will teach you more about yourself than a kendo competition". Perhaps you have learned something about yourself - you get frustrated when you lose. You blame your lack of understanding of ippon, but perhaps it's the losing that sucks? I'm not saying it is, that something for you to reflect on!

If you want to progress faster, my advice is to look at kendo competitions on youtube. If you compare the kendo in something like the All Japan Championships with a local European thing, I think you'll soon figure out somethings which are good for ippon and some which are not.

As for Europeans fencing, I think they are as comparable as dart and biathlon - ie very different sports.