@Vac-Efron I finally got it working. I think that there were several faults, but the last one was that in the dlclist.xml, at one line of 100ish the the line started with a capital I <Item> but ended with a small i </item>, I checked for this before, but apparently missed it. I downloaded this xml editor: https://www.oxygenxml.com/ which tells you if there is an apparent fault in the text.
Also I think that mod manager fucked up a little bit so I, because when i deleted some other mods (which weren't even activated) it started working.
I also found that the gameconfig that @FoxtrotDelta posted did not work for me because that the game crashed if I had more than two add-ons so this one worked for me: https://www.gta5-mods.com/misc/gameconfig-xml-add-more-addons
I hope that it works out if it hasn't already

Well, there is a mod manager, but it takes some time to learn and you probably want to backup your files anyway, but here it is https://www.gta5-mods.com/tools/gtav-mod-manager

well, still no luck. But I was wondering if there is anyway to get the old update folder? Since I use mod manager it would be very easy to swap between the old and the new folder, for when I'm playing online..

So, until the last update, all of my mods were working fine. But now, all mods except the add-ons work. I have been using Gta V mod manager and enhanced native trainer and I have the files in the same location as before. I have replaced the update.rpf with the new one and added all vehicles to dlclist.xml and extratitleupdatedata.meta, I have also replaced the gameconfig.xml. Whenever I try to spawn in a car it says something like "can't find model". I have tried to install the mods without the mods folder, but still no luck. I would need some help since I'm feeling that I have tried everything that I can come up with at least twice. Even the replace cars works, but not the add ons..

@Kenny_Loggins Have you found a solution? Because I have the same problem and it's driving me crazy...

I think that if you have the game on steam you can right click on GTA V in your library and go to properties>local files>verify integrity of game cache. I am not 100% sure, but I guess it's worth a try.