Modern Orhtodox is much more inclusive than charedism . When you are Satmar for example you are either 100% Satmar or 0% Satmar there really is no in-between. However Modern Orthodox is much more inclusive and includes people from those not much different than Charedi to those sort just hanging on and only marginally religious.
When you have a greater range of religiousity it does mean there will be more drop outs.