As someone who has used The Internet™ as a reference for more projects than I can count, I strongly disagree with this. There is definitely a middle ground where you know just enough to do some basic things on your own and feel comfortable venturing a bit deeper, but not without some help.
> It will not help you because bathroom fans may have different ways to disassemble them, car belts may have different bolts position etc.
I dunno, I can usually find at least one guide online for how to do a specific thing with a specific model of something. Search "change timing belt $year $make $model" and you'll get at least a handful of videos walking you through the whole process.
Having said all of that, this entire discussion is a bit moot because it's easy enough to download YouTube videos or tutorials locally ahead of time and pull them up on a tablet without internet access.
In theory, yes. In practice, I usually encounter new problems when fixing something that I need to learn. Kind of like Brian Cranston in Malcom in the Middle.