Modding it is hard. You need to unpack game files, install mods in a specific order which you almost never know, repack it and hope that it works. Alternatively you can install a merge (modpack made by other people) if you find one you like. Btw every update deletes most mods afaik.

But besides that there are a lot of mods and even without them I found the game pretty enjoyable. Just don't screw up the tech tree and you should be fine.

If you'd like some mod recommendations, I'd say 2013 vehicle handling, alternate gun sounds and a graphics mod if your machine can handle it (some require at least a 3060 for smooth gameplay). There's also Living City which adds a ton of customizable random freeroam events and features but that one is up to personal preference. I personally prefer a more vanilla experience.

Here is a video that sold me. They have merged mod packs that give Aiden new clothes, the living city mod kinda fixes most of the shortcomings of the game. It adds more missions more things that fit role of Aiden like gangs coming to attack you. A rouge like mode and even offline bots that will hack you keeping you your toes.