From what I remember you had to open the jar file with winrar or some stuff, delete some file in that and then place your mods in. Or you had to use a 3rd party launcher.
the current main way is using a 3rd party launcher
the old main way was to open the .jar file, delete the manifest file, and drag and drop in whatever files you need to
it really isn't that difficult, it's almost as easy as blockland modding
and there were mods to add in mod support, just putting zipped files in a mods folder
yeah if you're not going to mod minecraft then just dont get it, just a waste
but if you are go for it
even without modding, minecraft is a good choice
time spent is more based on the community of the server you find rather than the game you're playing, kind of like BL