I had two points regarding your assertions.
First, you can make the same argument (specious as it is) about any position drafted in the first round, as success (per your definition) rates are low for all of them.
Second, draft history has no predictive value regarding individual players. I have addressed this same argument with posters who cite the lack of success of QBs in the NFL that had sub 60% completion rates in college as a predictive indicator of Josh Allen's success/failure.
(1) The sample size of TEs drafted in the first round is too small to draw any significant statistical conclusions and (2) even if there was a large enough sample size, it would have no relevance whatsoever regarding whether or not Hockenson should be selected in the first round or whether or not he will be successful. Those are group statistics.
For example, if I told you that the average life expectancy of a male in the US was 72 years of age and that 70% of all men die by the time they are 82, it would not mean that you have a 70% chance of dying by the time you are 82 years old. As a matter of fact, it would mean nothing at all in regard to your personal life expectancy. That would depend on variables unique to you. Statistics might suggest that 70% of all men die by the time they are 82 years old; however, they cannot in any way say whether you are in the 70% that will die by age 82 or the 30% that will live longer.
It is the same with Hockenson. He will succeed or fail based solely on variables unique to him. The statistical analyses of any group of tight ends, or how well or how poorly any specific tight end played, or where they were selected in the draft, in the entire history of the NFL, has no relevance at all to Hockenson.