Technology

They aren't very good, and they probably can't be. You're limited by the laws of physics on what they can carry for their enormous size. The Hindenberg was the largest of them, but including passengers and crew together, it carried less than 100 people. They scale really, really poorly.

We can improve on old dirigibles somewhat with lighter weight materials and engines. We're ultimately limited by the volume of the lifting gas, and we're just not going to add that much more capacity. Even if someone figured out a vacuum dirigible (which would be very vulnerable to a puncture), it'd only improve things marginally. It's an interesting engineering challenge, though.

One thing where dirigibles might be useful is windmill blades. Blades aren't that heavy, but they can't get much bigger while being transported on highways. Constructing the blades on site is another option, so we'll see which one wins.

Science and engineering aren't magic that makes everything better over time always, and people need to stop acting like it does. There are physical limits that we can't breach. As another example, we haven't significantly improved on the drag coefficient of designs by Porsche or the Chrysler Airflow back in the 1930s. There was a design Mercedes came up with a while back that's based on the boxfish that did reduce it further, but its frontal cross section is so high that it doesn't matter, anyway. (It's also ugly as fuck, but that's a different matter.)