Is such useful today?
Absolutely so!
One case I read about was a British expedition to the Arabian Empty Quarter some time in the 1990's. They used electronic GPS units... Well they did not hold up in the extreme heat of the day and frigid nights and they had no directions out of the endless dunes. They would have been desert mummies had not a caravan of Tuaregs who could navigate by the sun and stars not found them. Saved and willing to go back, they then learned how to use this type of sextant, and carried several of these just in case their electronic GPS failed again.
The learning curve to use these takes some time, but doing so is worth it. I have used it to locate stars, and also measure the height of mountains. And it can be very useful in observing the sun during solar eclipses as it has a very wide field of view. I took another one for the total solar eclipse on April 8th, 2024 to observe the corona and prominences.
Now for those that do not know, this sextant is radioactive, and with a CDV-700 Geiger Counter it measures 4 mr/hr over the enclosed and sealed bubble chamber. And back then this was necessary to illuminate the bubble at times when the batteries in the holder were depleted on long flights. But today the luminous phosphorescent paint is much fainter than it was during the war.