After many days of observations and testing I noticed that one of the biggest problem with chunk loading is that despite slow chunk loading that has been "visually" fixed in 1.14.1 comparing to 1.14 - on the other hand - it greatly affected server-side performance. It causes TPS drop on the server and a big - up to 10 seconds - lag for other players upon someone's logging in and suddenly activating many chunks around. Similar situation take place if someone dies and respawns in other area.
If 3-4 players attemp to login same time lag is even worse and may cause server to drop TPS so low to crash the server. It is easy to recreate just running real server and simulate with just a couple of people dying or logging in and out.

Even much worse on 1.14.2 as described: MC-153239

UPDATE: about logging in lag - on 1.14.1 players login seem to be much better - still causing some lag but most of the time much less than it was before.