1. They feel too sharp
Sharp edges are great, when done properly. There is good sharp, and there is bad sharp. When a shop runs your skis across the machine side edge grinder to sharpen them, and they don't hand finish them, it can roll a bur from the edge, to the side of the base, this causes the ski to track straight and not initiate the turn easily.
2. Your skis don't want to start the turn
For many other reasons than number 1, your skis could be feeling too grippy, hard to start the turn. Detuning the tips and tails is a personal preference. (detuning means taking some sharpness out of the tips using a gummy stone.) Ski racers may not detune them at all, however, most people prefer a slight detune in the tips and tails to start the turn easier. Another reason is that your skis may not be flat. If your edges are higher than your base (which is not uncommon straight from the factory), your skis will want to track straight, making it harder for you to turn.
3. They don't grip at all, or grip too much
If your base edge bevel is less than 1 degree, your skis will feel like they want to catch. You'll feel like you're always on edge. Bevels mean putting an angle on the base and side edge. Almost a similar feeling than your skis being too sharp, but with a different cause. When bevels are uneven, they will turn erratically. If you have too much bevel, your skis will float and you'll feel like you never get a good edge. For most recreational skiers a 1 degree on the base edge, and 2 degrees on the side edge is optimal.
4. Ski feels slow and sticky
You are using the wrong wax, or worse: no wax. Applying the right wax for the right condition is critical. If the wrong wax is applied at the wrong time of the season, they don't glide properly, which will make them harder to turn. There are different waxes designed for different temperatures. Harder waxes are designed for colder temps, softer waxes are designed for warmer temperatures. There is a lot of science about additives and specialty waxes to make your skis perform at their peak. We recommend using Purl Wax for everyday skiing, and Swix HF BW for competition. Bottom line: the wetter the snow, the more important wax becomes.
5. Feel a vibration under your skis
Base structure matters. Most shops will put in a deep base structure because it looks nice and pretty, but really, a deep base structure is designed for softer snow. Base structure is designed to wick water away from the base. Which means cold snow requires fine structure for less drag, deep base structure will make your skis feel sticky in cold snow, and vice versa.
So now you know: your skis might not suck at all, it could just be the tune. Get them to a knowledgeable shop, who will take the time to properly tune your skis, taking all conditions into consideration.