Suspension can be complicated at the best of times, and trying to diagnose 'vague' handling in a car is always a fun topic for the morning discussion around the coffee machine.
From my personal experience (in other words, doesn't really count for much), 'vague' steering or handling at the front is almost always down to worn bushes or ball joints. The suspension bushes are basically the 'hinges' that the suspension components pivot around. Most vehicles have rubber bushes and the rubber perishes and gets brittle over time, allowing a little slack into that joint. If this happens on both sides, then the suspension arms will tend to move forwards and backwards a little under braking and acceleration, and laterally under cornering. Once the 'foundation' of the suspension is moving like this, the sense of vagueness creeps into the handling. The same thing can happen with the ball joints - normally either at the track rod ends (where the steering rack joins the hubs) or on the lower side of the suspension where it joins the lower swing arm. The same 'vague' handling will happen because parts of the suspension that are supposed to be rigidly tied together begin to have movement relative to each other (same as worn suspension bushes).
Neither of these jobs is particularly hard to fix if you're a decent home mechanic with the right tools, but most people will prefer to have a mechanic do it for them. Expect to pay about two hour's labour per wheel for a job like this. And then marvel at how much better your vehicle feels again, even if you can't put your finger on exactly why it feels better.
