But I am thinking recently that if the block size is increased, more transactions can be processed and the mempool will not be congested.
In a perfect world, yes, but from what we've seen in recent months this would only lead to larger Ordinals Inscriptions rather than an increased transaction throughput. Maybe someone can correct me if I'm wrong, but if I'm not mistaken the current congestion is largely due to Ordinals, rather than regular transactions.