Voyager was mostly (jetrel, resolutions) travelling in a straight line towards home. Well not a straight line as the crow flies, but they had a definite forward momentum away from Caretaker's Array.
This isn't very difficult.
The Kazon started attacking them at the beginning of season one, and gave up in season 3.
There is an obvious proportionate relationship between time and distance.
If you drive some where in your car, it takes a certain amount of time depending on how fast you are driving.
(I could literally be talking to a three year old right now, but when you ask me to dumb down my re-explanation for a third time because your brain can't make the connection, that's what you get. Sorry.)
Voyager had been travelling in a straight line ( almost) for 2 years before they were beyond the reach of the Kazon.
No one else using regular warp technology chased Voyager for that long or that far.
2 years = 2000 light years.
2 years = 2 fucking years.
The Kazon City Ships were not fast enough, and their empire can't have been big enough.
But still 2 years later, there they were.
In front of Voyager.
Just because we didn't see the Kazon in the episodes which they were not in, that doesn't mean that they cease to exist off camera where they were getting their shit together to kick Janeway in the nuts a couple episodes down the line.
26 + 16 + 1 = 43 episodes.
It takes the Kazon 2 years to cross space where they are welcome, or they outright control, that means that they have a massive empire or/and a lot of allies or they were bumbling around just like Janeway.
Almost every other empire Voyager chanced upon can be left for dust in hours or days, a week at the most, ie: One episode.
If it took 2 years to get beyond the reach of the Kazon, then every other civilization which they encountered that was more powerful and faster and advanced than the Kazon should have also taken at least 2 years to leave their field of influence... But that turned out not to be the case.