Exactly, and we should be HAPPY that we have this conversation. Happy that game UI and context sensitive controls have progressed so far that the need for a manual is almost gone.
It is far better to be able to play a game and learn by doing, with the help of tooltips and information directly in the game, than reading a manual on the side that often does not display the exact correct image to go with the text etc.
Heck, even old games like Alpha Centauri had an ingame encyclopedia with relevant game info, a manual within the game
I don't think it is just a case of games becoming easier and dumber, i think that is part of it in some games but i think the biggest deal is the massively improved user interfaces in most genres these days.
If in the olden days (SE4 as one of the most atrocious examples of poor explanation, nice gameplay though), you had rows and rows of buttons with no tooltips, no explanations, nothing.
Today in most games we have every single button and function explained to us right as we are about to press it. If a random event happens, there are clearly visible stats and effects visible as opposed to just "Plaguuu hits!!", leaving you puzzled until you flip to page 291 in the manual.
Frankly, it was not better in the past in this regard.
But it also means that an unfinished game really do need a little note in the main menu referring to the manual for things that have no been implemented in tooltips yet.
(looks at Sword of The Stars 2, with angry eyes)