Only now did Eren realize what Alephee meant when she said that he was swimming in the wrong pool when he was in Anfang?
Labh Salem was many times larger than Anfang geographically. However, the complexities it contained within itself were much more profound for someone like Eren.
He realized that the advantages he had in Anfang– the advantages he had fought so hard for– the advantages he had earned for himself through hard work and perseverance– almost didn't matter much in Labh Salem. This was because almost everyone else had them as well.
When everyone has the same advantage as you, it is similar to having none.
Tantras allowed Rankers to break even with the Practitioners of other paths. For example, most Rankers would have lost to Elementalists or the Soulweavers when it came to employing intent-based magic or making use of one's Spiritual Force.