So my group has been playing 2024 5e for a few months now, and I have run a variety of monsters from the new Monster Manual, and I've got to say, its okay.
After the OGL Crisis my group jumped the WotC ship and began playing a variety of other games. We played everything from AD&D 1e to Pathfinder 2e. We played many games and many campaigns. Most of the memorable moments for me came from clever play tactics from my even more clever players. We've had many awesome boss fights and cool stories. But you know what I don't remember? Looking at a stat block. I also don't remember any class features. I don't remember builds, even when they are my characters.
I remember players being on their last torch finding their way out of the dungeon. I remember clever tactics in combat and shield walls. I remember players befriending the hobgoblins in the Chaotic Caves because they knew they couldn't fight them.
As I reflect over past games and even take a pulse check on my current game (which has been an absolute blast), I really have tried to nail down why they were fun. I think my biggest two strengths as a DM are exploration and set piece battles. I really enjoy hexcrawls and dungeons using old school games because not only is there a procedure to it, but there were resources attached. I made a hexmap for my current game and we've done a few dungeons so far, and they have pretty quickly devolved back to what I found in 2014 5e, just me narrating room to room or hex to hex, then when players come across an enemy they mop the floor with them and repeat.
I could definitely add systems like tracking rounds and resources, but I think it elegantly works in old-school games because the other systems that are there are so fast and easy to resolve. Combat is basically the only thing heavily supported in 5e and it is anything but fast and easy to resolve. So tacking on another system to an already pretty complicated system just sounds like book keeping overload.
Another solution of the lack of tension in exploration would be to add random encounter checks. However, as previously mentioned, combat takes a while, so coming across one or two random encounters and there goes 50% of the session. It works in old-school games because combat is just as easily resolved as searching a room.
When it comes to combat, I really do like set piece battles. I am a sucker for a boss room, specific boss battle music, a big mini and MMO style mechanics on a raid boss. 5e does this pretty well. They fought a manticore-like beast recently in a toxic alchemical wasteland and it was a really fun. He was flying around, doing manticore things. They also fought some bandits a few times, and it was kind of just a slog. No fault of any of the players. They were being clever, commanding the Ogre to run away, positioning well, doing all the things. But as the DM it was just roll, 3 damage, move a little, hide in cover, repeat.
The advice here is give alternative goals or environmental things. For every combat? That just honestly feels like more to track, which ultimately doesn't change much. I distinctly remember a boss battle in Shadowdark that took place as the party and their allies were storming a hill that was controlled by an Orc chieftain and a necromancer. Both statblocks combined probably fit on an index card. But the party was in a shield wall, slowly advancing on the enemy. Then when the wall broke they swung around and took the "bosses" on in a more 1v1 battle. It was awesome. It was also insanely easy to run. The game got out of the way, I barely referenced the stats because the actual in fiction actions of the enemies were much more important, because of their lack of "mechanics". Hell, we spend a chunk of combat just looking up and referencing the rules.
I am definitely not dissatisfied with the campaign. I love the characters, the story, the world, the bad guys, everything. I don't know if I'll come back to 5e however. For now, I'll stick to cool story beats, focusing on the character's individual stories, and boss battles to the Doom soundtrack.