The MCT is not the actual time it takes passengers to transfer from terminal to terminal or gate to gate but more about how the airlines and airport coordinate their activities e.g. getting bags moved around and their arrivals / departures schedules and what they feel comfortable with plus a little leeway to allow for a delay on an incoming flight.

If the airlines didn't feel the (in your case) 90mins was sufficient then they wouldn't offer that flight combination to passengers on a single ticket.

The vast majority of people do the physical transfer in a lot less time than the published MCT and catch their flights with no issues- including being at the gate at the required 20-30 minutes before doors close.