As someone who is DMing for an Open Hand Monk as one of two martials and two spell casters I can say monks definitely are really good in specific aspects of combat. But in all other aspets they are very subpar compared to other martials and casters in the party. Whenever mobility is needed for example, this is where they shine. They are also great in breaking concentration with their many attacks.

So I try to create many encounters to cater to them. If I make a medium sized square room with 2 tough enemies then the monk is just a worse fighter. Run up and hit isn’t what makes them good.

Instead I make encounters with large arenas, where there are enemies spread out who need to be taken care of. Such as caster who are concentrating on a dangerous spell but who are far away and spread out, maybe even behind cover. Or I have very mobile enemies which are hard to pin down for other melee combatants. Shooting monks with ranged weapons is also fun due to deflect missle. It works and the monk regularly has their moments to shine just like the others.

But the monk is the only one where I have to put in specific work to play to their strengths. This to me clearly indicates that monks are not as good. They are fun and can be made work though which is great.