Sounds like he had no idea how to properly add mods.... I had a fully modded Oblivion and there were no problems what so ever.
Mods are completely worth it *if you download the right ones and dont just download lolanimearmor* it makes the game so much more enjoyable.
Unless, of course, you enjoy "lolanimearmor".

The key is to find mods (from among the thousands and thousands, covering nigh-infinite topics) that you enjoy, and take the time to install them correctly.
Yes, as with all amateur work, some have flaws. And, of course, they can conflict with each other. But that doesn't mean you can't find a good set of mods that work well.
