Back in the days of NHB people said this, and to a large extent they were correct- but for the wrong reasons. The reasons used for jabs/kicks/striking in general "not being effective" was that the techniques were flawed, even though some people argued against them, they were the minority.
The reason they weren't effective was because the chances of you having good striking and staying off your back were slim. Also, if you had good grappling, the chances of you having a good jab were just as bad. It wasn't until after time limits, weight classes and the well-rounded fighter came into being that we saw these techniques being used effectively.
Yes, I remember the dark ages.