With all these planets, why haven't we found any exomoons?

The article explains here, "New research suggests that one reason we haven't confirmed the detection of an exomoon is that our detection methods favor larger planets closer to their stars, which are far less likely to host moons in stable orbits."

My observation. A simple answer here that seems very correct. At the exoplanet sites, for those with orbital periods <=370 days, there are some 3900 or more shown with short periods, and many with large masses.

This exoplanet site shows 3930 planets with short periods <=370 days, The Extrasolar Planets Encyclopaedia (exoplanet.eu) The average period is 29.46 days.

This site shows 3811 planets with average period 28.49 days, NASA Exoplanet Archive (caltech.edu)

I can routinely observe the Galilean moons at Jupiter using my telescopes (90-mm refractor and 10-inch Newtonian) but seeing exomoons like that, is a work in progress :)
It’s hard enough to detect a planet orbiting another star, with the bright star and dim planet and so close together. Some are detected by the change in magnitude during occultation, some by the gravitational wobble of the star. It would be way more difficult to detect an even lower grade wobble of a planet we can’t see, and if a planet occults the star, we get the combination magnitude of the planet and the moon together. Just remember, we didn’t know Pluto had moons until 1998.