You want a better campaign?
Keep it limited.
It's already in the air. One or two 5th edition books a year. Pathfinder creaking like the bounty after their overly excited engineers got ahold of it and thought adding just one more feat sixty times would make it better. The fact that she was sunk two years ago is just a WEIRD COINKYDINK.
One of my players said, "Can I use the Princes of the Apocalypse spells in your Tyranny of Dragons campaign?" I was like "NOPE". Whaaaaat? Impacting agency? Am I being a jerk?
You want a good campaign, keep it limited.
7 races. 7 monsters. 7 significant NPC's. 7 forces. Seven schools of wizards with seven spells per level. Seven fighting styles. Seven ancient lores. Seven great weapons.
- Feral Halflings
- Implacable Giant Bear Monsters That shoot fire beams from their eyes. (Secret surprise, they turn into sharks.)
- Giant Toads
- Tribal Carnivorous Apes
- Acid Weasels
Can you see that campaign in your head? Is it memorable? The starred races are the ones the players can start as. The others would have to be unlocked. This isn't generic. It sparks the imagination.
Part of the issue is that this either happens subconsciously, in that we tend to focus on the consequences of the encounters we have, in the future. What this ends up looking like in play, is that there's the main thing (we keep running into X) and then a bunch of random one-offs that never have time to shine. Having all those random one-offs being in theme makes things more interesting in play and brings a great deal more cohesion in the campaign.
Another example, My Tyranny of Dragons campaigns has: Humans/Moon Elves/Shield Dwarves/Lizard Men/Orcs/ and halflings for races. It has Dragons/Drakes/Cultists/Giants/Bullywugs/ Kobolds and Hobgoblins for monsters. Cultists and dragons are divided into 5 types.
If you have a wandering monster table with more than 7 things on it, the chances of encountering anything more than once is vanishingly rare, meaning the area is less thematic. I'm not the only one talking about this. But I'm the one that's saying, let's look at the numbers.
If you have a six hour session, and you roll for 1 in 6 random encounters. You check that die somewhere in the neighborhood of 20 times. That means about 3 random encounters. On average, with 20 entry encounter table, you'll have 6 encounters before there's a 50% chance of duplicating one. That's a 50% chance of getting a duplicate encounter every 2 weeks of play. Not very thematic or consistent. If your table only has 3-5 entries, that threshold drops to 3 encounters.
There's more to this too! If you're using a spoor system or an overloaded encounter die, then the results become more significant, because the players will really become familiar with these monsters. These monsters and their interactions can be fleshed out, creating a more complex ecosystem that your players are adventuring in. Add in 4 lost dead races (for different kinds of ruins) and some different factions (tribes/cults/etc.) that your races are a part of, then you have a strongly themed adventure.
Obvious benefits are that when you do include something from out of theme, it will really make an impact on your players. Most of the campaign builds itself from the juxtapositions in the limited list. You end up with a world that doesn't feel like generic fantasy. These seven choices aren't forever. Most campaigns last from 3 to 6 months. Instead of changing campaigns, as yours evolves, you can change this list!