Whilst certainly some players can play effectively with a 90 second turn time, others can't. To which turn times of 90 seconds min disclude a number of players from taking part in this game mode. This is true for experienced players, never mind new ones.
Speaking of which; there's hopefully soon going to be a new group of players joining CR as a result of the free steam keys given to Phoenix Point backers. Those players (assuming that they're from an X-com) background are used to playing a slow tactical game, not a quick time limited one.
With an increased time limit for duel matches,imho it should be 2 mins rather than 90 seconds, you've a better chance of retaining those players than with the current time limit..