New Campaign Makes Old One Suck

I recently started to run my new campaign with a group I played with about a year ago after months of preparation (along with a new player who has been great). The first few sessions (while short) have been great and I’m really excited to explore the world and their characters.

In the gap between campaigns I joined another as a player and am still playing in it. It was pretty fun at first, was playing with two friends (one was a dm), my girlfriend, and two strangers. Then me and my girlfriend broke up, so she left the campaign, but still the campaign was fun.

Recently though, I’ve been noticing the combats feel very scripted / swingy. Like an enemy will get hit a few times and be described as barely injured, but when we start losing the fight, the next hit will kill that enemy (or put it on deaths door). Similarly, movement speeds of enemies and their reaches seem to always be oddly but perfectly apt (10 foot reach on a fighter with fists, a dude with 35ft of movement). Creatures also just have random features like a rogue who was immune to frightened or a fighter that was able to just end a spell or magical effect and an elf who just had an innate flying speed with hover.

We then reached the halfway point of the campaign, where we kinda lost because our original goal was actually helping the BBEG and we learned that we needed to now stop him. He trapped is in a demi plane for a few days because we wouldn’t side with him.

One of our party members left due to scheduling and we got two new replacements. One of them straight up just didn’t show up to session and our forgot to give the roll20 link to the other so he made his sheet on dnd beyond and had to manually roll the whole session. He also just kinda tried to be really quirky and make jokes the whole time and would interrupt people with random unrelated tangents. He also tried to force us to get married to him with Ceremony to get +2 AC.

I just felt kinda sidelined the whole session and was constantly thinking how I’d much rather be playing my own campaign right now. I supposed it didn’t help that I kept getting knocked down to 0 hit points just before my turn started so I only had 1 turn in combat all session.

So yeah this was kinda a vent / rant but also I kinda want advice. Has anyone else experienced this where one good campaign makes the other one seem so much worse in comparison? If so how can I get around this feeling?