Don't measure experience by how long someone's done things. Measure it by what they've done. It's that old quote about "10 years of experience, or one year of experience repeated 10 years."
I've also been following this individual. I don't tend to agree too much with what he has to say because my experiences are very different.
I met a dev at a meetup the other night as I was giving a talk on Elm. He's been doing web dev almost as long as me. He still does HTML with tables. He uses inline CSS. He's never investigated a preprocessor, and has never looked at Angular, Backbone, or React.
But he's successful, so, shrug.
So be wary of "appeal to authority" arguments. Yes, he's been around a long time. Doesn't mean he's right.
None of us are really right. Just weigh all the opinions and decide based on experience.
I'm too old and tired now to try to convince people I'm right and they're wrong. I'm more interested in saying "I think this is cool and here's why."
For the record, I think Elm is the future and you can pry Sass from my cold, dead hands. Those are just my opinions, and they may change. It doesn't mean anyone who uses jQuery and straight CSS is wrong.
We can only say that it's "holding him back" only if we can show that he doesn't get the same results as SASS users, in the same amount of time.
We think your path is the wrong way and will cause you problems as time goes on.