Random latency lag spikes 200-2000ms, especially when fighting monsters, WinMTR included

I've found a program called "ExitLag" that solved all my problems. Now, of course this is not a free program, so I may still decide to call on my ISP later to see if they can do something for me for free.
Just out of curiosity though: if the packet loss starts at an early node like my router or ISP, and is the reason for my lag spikes in game - is it really possible for a pathing program like ExitLag to fix the issue? The packet loss should still be there regardless right? Or does this hint at my router and ISP packet loss not being the main problem afterall?

Edit: nevermind, I think I just got lucky or something. For two or three instances there were no problems at all, but when I tried playing again later on, I had the exact same problems even with using the program (and sometimes it actually got even worse than before)