To mod or not to mod...

[user]

If you didn't start playing games yesterday and are able to know how the mod you are adding will change the game, there is absolutely no reason not to mod from the get-go. As simple as that. So no, no reason to play vanilla and put yourself through a sub-optimal experience, unless you are certain the game is flawless the way it is.

So how would you know what to fix to your liking if you haven’t experienced the game already? For example I use a very simple mod for Morrowind that requires you to get 15 skillups for a level up instead of the usual 10... I tried the game and simply not worry about multipliers for levelups that felt like the most natural thing for me.
Other players try to go for the least used skills on their build as their main character skills to make sure they level up on their terms, seems like a very complicated way to do so but you only get that knowledge and preference through experiencing the game and then making your mind up on what exactly you want to change

If you are the one making the mod, you 100% need to play the game thoroughly. And sure, when you use mods and it comes to fine-tuning stuff like that, knowledge of the game will help (even though you don't need to play the whole game).
But many changes are far more obvious and usually explained in the mod's description. You can also tell more often than not where the modder is coming from. For example as soon as I read OOO's description for Oblivion, Ghost Mod's for W3, Requiem's for Skyrim, FWE for F3, or BCIC for kingdom come and saw what they did, I never looked back.

 

[Reader]

Unofficial patches - great.
Widescreen patches - not necessary but good. Was great for me in Sacred Gold which refused to launch with black bars for some reason.
Visual mods - shit. "I am more talented designer but also have no job" Never works.
Balance/gameplay mods - same. Even worse. After all these years Skyrim is still mediocre at best.
Total conversion mods - Enderal.