That's how ethereum started with such low gas fees nd fast transaction. But when it's network got conjested we started seeing insane gas fees and traction finality time getting slow, same thing might happen to BSC, the more it's network gets loaded, the more it's transaction fees will keep increasing, this is more reason why sharding is very much important, no matter how fast  a blockchain is, sharding is important for a blockchain which is ready for mass adoption, take the Near protocol network for example, in absence of it's low fees and fast transaction there are still launching a nightshade to boost it's network capability, this shows they are ready for mass adoption.