The Radziner thought the cuttlefish was the chilazon. I won’t go into it, but it was proven that that he was fooled by chemists. Since then, Many rabbonim simply don’t want to get involved in the topic because they are afraid to be proven wrong later.
I am not a Rov but I know how to learn a little. A number of years ago someone from E.Y. spoke in our shul about trunculus. I decided to write a maamar disproving him. After studying the topic in depth instead of writing the maamar, I started wearing it myself.
There are many many powerful proofs for this being the real tchelles. This is not the venue for going into all of them. I will share with you the strongest one.
There are ancient dyeing factories in northern E.Y. and Lebanon with ditches full of – not millions – but hundreds of millions of empty trunculus shells. There is no question by anyone that truclulus extract was used as an ancient dye.
The gemara says that Indigo (Kla Ilan) is so similar to Tcheles that the Ribono Shel Olam will punish someone that substitutes Kla Ilan for Tcheles from chilazon. (kla ilan – originally grown only in India – is much cheaper than trunculus extract – which is why trunculus fell into disuse eventually.)
Now, indigo dyed wool and trunculus dyed wool is so very similar that it is impossible for anything other than spectrographic analysis to tell them apart.
So if it is true – as some want to say – that trunculus is not the real tchelles, there must be another marine species that has an extract also similar to Indigo and trunculus. In that case, why didn’t Chazal warn us also about this other imposter – trunculus – which was very well known as a dye in ancient times and whose extract is also exactly the same color as tchelles?
You want to know why they didn’t? Because trunculus IS DEFINITELY tcheles. That’s why.
I am not even going into the numerous other proofs.
BTW every year more and more rabbonim, some very choshuve and well-known, are starting to wear this tcheles. Some open, some btsin’a . If you ask anyone of them that doesn’t, you will find that, for the most part, they simply don’t want to deal with the whole issue.