You missed my point. You are not following standard Linux practice which is
to install from the repositories. There is nothing wrong with that if you
are prepared to suffer the consequences and accept the blame. Instead you
are sticking hairpins in electrical outlets and then blaming the electric
company. Many users like to install from source code and binaries, but if
you do this then what you do becomes your responsibility.

Your problem is not an Ubuntu problem because you went outside of the
repositories. They go to great trouble to set up repositories. They go to
even more trouble to package the restricted-extras for each distribution
they make. When you fail to use their repositories and then fault Ubuntu as
you have done then you are misplacing blame. People who install Ubuntu and
then add the restricted extras can use Youtube without a problem.

Now, you need to remove the old flash binaries that you installed before you
can get back to square one. Then you can install the restricted-extras. To
remove your binaries you can use Synaptic. Go to Status, Installed local or
obsolete. Remove flash from the list. Then install the
ubuntu-restricted-extras.

No distribution is above criticism. Just make sure that it is deserved
criticism. In this case it is not. Flash works in Ubuntu. You can install it
in one easy step by installing the ubuntu-restricted-extras. The Ubuntu menu
also works just fine. When you install an application from the repositories,
it will add a menu item, provided it is meant to be run from the menu. If
you install it from outside of the repositories or alter the location where
it is installed then it won't. If you manually install something then you
need to manually edit the menu.

I am sorry if I sounded harsh in my criticism. I don't much care for
assigning blame in the first place and when it is misdirected then it rubs
me the wrong way.