Why "konnte" here? Why not just “kann”? Is the narrator emphasising that he had a system at some point in the past but not anymore?
The problem here is that you interpret "[...] konnte ich [...] erkennen." as the description of a state (seeing a system), when it actually describes an event in the past that marks the transition from one state (not seeing a system) to another (seeing a system).
Your interpretation is not wrong:
There was a time span (that is over now), when I was able to see a system.
But most German native speakers will understand it as:
There was a point in time (in the past), when I started to see a system (and I still can see it).
I don't have a source or rule, but from my intuitive understanding I would say that the latter interpretation is what comes to mind first when the topic is about identifying something or learning something.
If you wanted to express in German what you understood, I'd phrase it like this (but this might be colloqiual, not sure):
Irgendwann konnte ich mal ein System erkennen.
or more explicitely:
Bis zu einem gewissen Zeitpunkt konnte ich ein System erkennen.