There's no "wrong" way to knit. If your finished project looks good to you and you're happy with the process, then it's not wrong.
However, if you find an easier way to do something, it certainly might be worth changing your method!
I do both "regular" and combined knitting, depending on what I'm working on--for rows and rows of flat st st, I'll often switch to combination (even though combo knitting requires doing the decreases different from what's called for in most patterns).
When doing ribbing, I have started using a mixture of combined and regular knitting because it makes my ribbing look much more even. If I go just the regular route or just the combined route on ribbing, it looks awful! Lots of rowing out.
So all in all, what you learned the first time isn't necessarily wrong, nor is it a waste of time. In fact, it will probably come in handy some day!