The only classes that can stand on even ground with a wizard or druid (that I know of) are artificers and clerics.

Unfortunately, you are correct. The quickest way to power in D&D and Pathfinder is to have a spell list. In Tome of Battle, which is considered by some (including myself) to be a "patch" for martial characters, a maneuver system was introduced. This system does have some similarities to spell casting, but it works more on an encounter to encounter schedule rather than a day to day one.

The idea at the core that both of these systems is utility. If something isn't working, you can do something else. Instead of constantly hitting the dragon with your axe, you can switch to a spell or maneuver that you think might work better.

I'm no expert, but from what I've read and seen in this game, utility/options=power.