Catchers typically progress slower than players at most other positions. The average time for a college catcher to make it to the majors is 4.15 years. The average for a high school catchers is 5.27 years. This time can be reduced if a player has a higher skill level. Elite players only take 3.04 years out of college and 4.09 out of high school. These are averages. It's not to say a prep catcher will take 4 years. Joe Mauer took just over two years but usually catchers don't make an impact until they are 24-25.
On average, each MLB team carries three catchers throughout the year. A starter who catchers 116 games, a backup who plays in 62 and a 3rd catcher who gets into 15 games. Actually, over the last 5 years, MLB teams have average using just over 1.5 players like this. So most teams should have 3 catchers on their 40 man roster and most likely rotate one more through the roster annually. The averages don't account for them playing other positions, only that they are primarily catchers. This is a position that very little offense is required to be a major leaguer if they defend well enough. They also can play at a later age than many other positions, as long as their body can take it. Experience and knowledge is a neccesity behind the dish. It takes time to get the reps to acquire the knowledge and skills. That is why many catchers become good managers.
Catchers have the most reponsibility of any position on the field and are the only position to be able to see the game unfold in front of them. It's a unique position that takes a certain type of player to succeed at. It is rigorous and difficult and very hard to stand out as. The players that succeed are usually flawed players based on tools and offensive stats. They are typically slow, have below average speed and usually don't have impressive bats or on-base skills. If they do, they are impressive. That is why players like Reese McGuire are so tantalizing. The bat could be very good, as well as the defense. That is also the reason to be excited about players like Nick Ciuffo and Max Pentecost who have average skills across the board and look like they have the skills to stick behind the dish.
Using stats from 2009-2013, here are the positional averages.
This is to give perspective on how many MLB players come from each age group. I hope it shows how amazing even backup players are. You have to be a special player to make it to the majors and the best of the best to be good. Most ages only have 2 or 3 starter caliber players. It shows how much of a success it is for a team to develop a player to get them to the majors.
Age 25 and Under