Well yeah...But theres also more specialized pages + hybrid pages. In general for AD or AP you can do 21/9/0 taking the AP or AD masteries respectively. For tanks 21 in defense is good the rest are up to you.
You could probably play most standard mid AP champions with 21/0/9. For AD there's either 21/9/0 (armor and health) or 21/0/9 (mana & regen). All damage reduction masteries are nice for the first jungle clear. For supports, 9/0/21 (CDR) or 0/9/21 (more tankyness) is nice, although some tankier supports (Leona, Taric, etc.) could probably benefit greatly from more points in the defense tree.
AD carries and standard AP mids probably work the best with a single mastery page for each.
Solomid.net has guides for every champion, itll give you a good place to start. Alot of it is preference though, AD carries and Assassins should pretty much always go 21 in offense. But other then that its really up to you, Supports can go 21 in defense to be tankier or 21 in utility for the bonuses that gives you. Bruisers can pretty much do anything they want masteries wise. Play around with em and see what you like more.