NO major American Kashrus organization follows Rav Elyashiv’s psak regarding worms in the fish, mainly because they contend that the metziyus was not presented to Rav Elyashiv properly.
Techeiles requires far more detailed technical knowledge than the question of anisakis in fish.
When taking about “most poskim”, it’s important to the refer to most poskim who went through the Sugya.