Laval is not a good deck even though it relies on one of the strongest mechanics and that with skill (no tear has no skill its gamble) (no mayonesse is not a deck)

but why is it bad if it has cards that other decks can only dream of?

well, some monsters are really strong and would be a wet dream in other decks, but in Laval... oh dear, the best monster was banned because it was generic (beginner mistake Konami, you can do better!)

and the extra deck of the deck is not only ridiculously expensive in MD it is also horribly bad

even the newest synchro monster is laughably bad negate? pah no! destroy and burn damage? YES

and it has rekindling as an effect! is quite nice for link plays? but it doesn't have its own link cards so you have to be boring and resort to generic links Apo and all that stuff

otherwise it works with banishing cards so you could play D.D dynamite I think

what is it about pyro/fire decks that make them want to burn damage and banish themselves? (except boring eyes and Dino 2.0 i.e. fire kings)

laval's strategy is burn damage and synchro spam very slow synchro spam

what laval needs is a good extra deck that works more to improve the burn strategy or more with banished cards since you banish your own cards more often after targeted mills

So basically only 2-3 good cards have to come and Laval could achieve something