The round system in boxing makes sense. You start standing and ending the round doesn't really cause you to lose any valuable positions. You could have someone stunned or trapped against the ropes but you're still standing.

In MMA however, ending the round can cost you valuable positions. In a match like Rani Yahya versus Chase Beebe, Rani had Chase in a submission hold at the end of the round but the round ended so the fight was stood up. Chase went on to win the fight. Now theoretically Chase is a less exciting fighter on Rani as he is primarily a wrestler with cardio. If there was over time in the round Rani could have had the opportunity to win. The most exciting fighters are finishers(submission, muay thai clinch, dirty boxing finishing, knockout power strikers, ground and pound fighters). Over time in rounds would help favor more exciting fighters.

There's also the anti-climactic element. A common phrase thrown around is that sometimes the knockout is merciful. Sometimes fighters get knocked down or suffer lots of damage from the mount and then the round ends. Either, the fighter on the receiving end gets finished anyway in the next round taking needless extra damage or the fighter on the punishing end gasses out and the other fighter barely wins the decision due to the 10-point must system.

There are good things to the round system. It gives fighters a one minute break to keep cardio up so fights are more exciting and it allows the corner to help adjust the game plan of fighters in between rounds.

There's an easy solution to maintain the positives and the negatives of the round system: over time. The round can only end in a position where the fight would be stood up, separated, or when a referee would call for a break to cut tape or put back in a mouthpiece. The round would continue until the fight finishes or they get into a position where the referee would call for a break in the action.

As for the problem of scheduling fights that can go on for longer than scheduled, there are already similar situations like knees to a downed opponent, eye gouges, or low blows. How they handle that situation is that they give time for main events to run long and then show preliminary fights if the fight doesn't take all the accounted time.

The round system has positives and negatives but is easily rectified by adding in over time.