First off they are only fixed if you let them be. Granted it requires a file or a welder to make adjustments but you CAN adjust them.
OK, assuming it's an elevation only issue. It's all just down to the ammo. You don't say which gun it is. That would help a lot.
In a revolver such as a S&W Model 10 they are intended to shoot with the classic .38Spl load of 158gn cast pushed at around 850 fps. But the key is the 158gn bullet. After that cast or jacketed can be fudged for muzzle speed to match the sights. 148gn wadcutter loads are the other classic which works with these sights due to the lower power level to go with the lighter bullet.
If it's a cowboy style SAA clone then be aware that often the sights are copied off the old .45Colt sights. Other calibers such as .357Mag chambering has more weight in the barrel and cylinder due to the smaller "holes". And they didn't always put in the proper height of front sight.
Regardless of what it is (please tell us, I'm deing to know

) if it's hitting below your POA then it's likely that the maker left it high on purpose because of ammo variations. You need to settle in on a load you like and THEN trim the front blade for height to match the aim to the ammo's POI.
If it's an SAA then shooting one or two handed also plays a part in all this. So keep that in mind.
If it's an SAA then your hand position will affect the windage. If you try to use a high hold like a modern gun it's going to want to pull strongly to the left. You want to use a hold which puts the web of your hand over the rear strap just at or a touch below the middle of the bend at the top. Any higher and it'll pull left. If you wear medium or larger gloves usually then try putting your pinky under the butt of the grips instead of wedging your hand up high to make room for your pinky. Pinky under is actually how these are intended to be held for all but those with the smallest of hands.
Once you settle on your hold style and ammo bullet weight and power level then it's time to trim the front blade down with a file if it still shoots low. If it's shooting high then you either live with it or alter your reload power level or bullet weight. Heavier or slower shoots higher. Lighter or faster shoots lower.
If you need a SLIGHT windage correction and a few other folks have shot the gun and it's consistently off for all of you then you can open up the rear notch on one side with a needle file then touch up the bluing. Don't go crazy though or you might open it up so much that it's hard to gauge the gaps to either side of the front blade in the notch. While this is OK for action shooting and in fact is a nice thing to do it's not good to go over board for a bullseye gun.