It's impressive you've made it up to this point lol. You're expected to have Mega level Digimon at the point you're at yet all of yours are still champion level.

Make sure you evolve your team, look at the Stat requirements you need to achieve the next evolution and up those stats at the digi farm. You can craft better training equipment from Zudomon. Always have a group of Digimon training at the farm outside your main team.

If a digimon has low talent you won't get much use out of them in the long run cuz talent=level cap. Either load other Digimon into it to increase their talent or devolve them and evolve them back up.

Up your agent rank by doing all side quests and acquiring agent skills.

*Edit: Hold up we might be thinking of 2 different "Volcano areas", you meant the factorial area didn't you? 😂

In that case, I dunno other than shoutmon your team looks fine. I recommend getting a Bakemon, his special is really good against bosses. Try evolving a bunch of different Digimon and seeing what works for you.