For the most part, this is true. Most scouts are, unfortunately, so addicted to sheer speed that they won't even take a second look at guys who don't throw 97 MPH or faster, and as a result they will miss out on the finesse pitchers who---in my opinion---can be the deadliest of the lot. Take the case of Eddie Lopat. He hardly broke 90---not even ordinary fast, so he relied on control, command and an ever-expanding arsenal of offspeed and breaking pitches. He was pitching in the minors---the AA Southern Association---and the scouts weren't even mildly interested, because he didn't have a fastball worthy of the name, and it took the president of the league---a former major league umpire---to get anyone to consider it. This umpire finally got the Chicago White Sox to take a look at him. The Sox agreed to take him on a 30-day trial basis (most unusual), and when he started winning games---especially against the Cleveland Indians, who were then a very good team---they decided to keep him.
The rest is history. He pitched for the White Sox for four years, and the Yankees got wind of what he was doing to the Tribe (and several other teams) and kept an eye on him. What they noticed was the walks: very few of them. One walk every five innings, if at all, and they decided they just had to have him. So in 1948, just before the start of spring training, they acquired him in a trade---and he went from being a good pitcher with a lousy team to a very, very good pitcher with a great team. He spent 7 1/2 years as a key member of the Bombers' fabled Big Three rotation and was part of the "October Twelve", a dozen players who were instrumental in their unprecedented five-year World Championship run.
He was a finesse pitcher who, it seems, threw everything but the kitchen sink---and the Indians called him every bleep in the book because they couldn't beat him for sour apples. And from time to time he would throw a knuckleball. Just to be cute. And since then there have been some very good finesse pitchers (think Jamie Moyer). It just goes to show you: the scouts don't know everything. 8)