Just a few thoughts here.
First, thinner picks have a lot more pick clack than stiffer/heavier picks. In general, beginners start with thinner picks and as they get more experience and control they move to heavier picks. Anyone annoyed with pick clack might simply try heavier picks. Your playing will become a bit more precise in the process.
Second, you can minimize pick clack (but not get rid of it entirely) with a different technique. Hold the pick loosely, not tightly in your hand, and think of it as gliding over the top of the strings rather than getting into each one and really plucking it.
Third, some folks claim that pick clack always sounds louder to the player than it does to the audience. I supposed you could test this by making a series of recordings with the mic in different places, but I've never tried myself.
Fourth, a leather pick (or those felt picks that some uke players use or even rubber picks that I use for an acoustic bass) would all have less pick clack than a plastic pick, but that doesn't mean they are equally versatile. Although I think you could probably strum OK with a leather pick, I am not sure you would have the control to flatpick, meaning playing long single-note runs. So if you always strum across all the strings it might work OK, but if you want to play a fiddle tune or a filler lick the leather might not provide enough precision.
I encourage everyone to experiment with as many different types of picks as possible. Eventually you will find the one for you. I use a standard guitar pick (the Dunlop Tortex picks) and the only ones that I prefer more than those are way too expensive (like the BlueChip picks that range between $35 and $75 for a single pick!
).