Actually 4 seam FB movement is critical to the pitcher's success which is why Kelly throwing 100 is usually still a fail. His FB simply leaves his hand and finishes where it started. If that is the 4-seam FB you have it does not matter how hard you throw it, hitters will catch up to it. That said, his curve does not do a darned thing either.
The reason the rising 4-seam is successful for example is because it starts in one place and finishes in another. The hitter simply can't lay off the thing if it has enough movement. It is difficult for the hitter to deal with a pitcher featuring a 2-seam and 4-seam because the 2-seam bores in on the RH hitter from the RH pitcher and the 4-seam rises. If said pitcher can combine those with a hard sinker away, he might not have to throw anything else all day long. If said pitcher can successfully mix in a change, he might pitch a perfect game. The cutter add a little more variety to the mix but its usually used by pitchers that can't throw a 2-seam inside without hitting the batter.
At least IMO the hardest thing in organized team sports is hitting the competently pitched baseball from the best pitchers your particular level of play has to offer. How MLB hitters do it at all is beyond my feeble talents and even in some ways beyond my feeble understanding as is the case for all of us that have not been there. Having the hand/eye coordination to recognize what is coming and combining that with the physical quickness needed to get the bat to the hitting zone against the variety of pitches and quality of the ML pitcher is simply something otherworldly. Take it for granted that all hitters are trying to think along with the battery and all hitters should be looking to narrow the hitting zone down to something they can drive with less than 2 strikes.