You're definitely not alone in this boat. Most of my mid/late game is about juggling XP on multiple characters. It gets even worse when you need to trigger a specific event for a quest (that's usually a skip, otherwise you can get stuck for a long, long time). Note: please remove XP events from quests until we can realiably trigger them

As everyone else mentioned, when stuck, go through the list and try all the XP events. Do quests as well. But go through the list, don't ignore that.
My few bits about XP maintenance bellow:
- Stop worriny about LP unless you have to.
- Make a list of XP efficient curios that you can easily craft/get. I usually prefer 700 - 1000 LP / XP, some can be much higher, like 20 k LP / XP. q100 eggs are a decent core of this strategy, pretty much free curios and all are 1000 - 1500 LP / XP.
- Hard avoid XP traps like cigars, great wax seal and others.
- Swap characters when doing chores around the village.
- Watch what XP events trigger and when, learn the list, try to trigger everything you easily can.
- Build your gameplay around triggering XP events - when it's dawn, move all your characters outside or even to a mountain, when designing your village, leave some grass tiles in for the free XP you get from walking over them without thinking, let all chars open the ovens/smelters when you're baking/smelting, keep dead bodies and bury them every once in a while, don't forget to put flower on the grave etc.
- Learn when and what triggers, there's a system to this madness and you can fairly realiably cycle few events to maintain your characters.
- Do quests when stuck or desperate.
- Do dungeons. Ant and higher can have XP dreams in them iirc, that's usually 500 - 1000 XP per dream.
- Focus hard on your claim holders, never let them run out of XP and do not overdo it on studying on them. Focus on maintaining the claim, not growing those characters, if you're worried about XP.
- Keep dead bodies and bury them every once in a while.
- Plant trees every day.
- Buy XP dreams - worst case scenario, you learn nothing by doing this, but it can help when you're desperate and your claim is running out of auth.
The current XP system is punishing anyone who focuses on just a few things. Our herder is always out of XP 'cause she only works with animals and processes our cheese. That's not enough to sustain her XP as she gets locked and can't really reset her queue just from these activities. The more varied your activities are the higher the odds of you accidentally reseting your queue and getting enough XP to sustain yourself.
And whenever you feel frustrated, remember that you're not alone. This system frustrates a lot of people (especially the credo quests), but nothing much has changed over the years, so don't expect any changes anytime soon.
Everytime I find something that doesn't make sense I can almost see Jorb grinning and mumbling to himself: "working as intended."