I guess it all depends on your style and what part you play in a group.
We have an acoustic guitar strummer who uses a thin Delrin pick, and mandolin player who thrashes with a thin Delrin pick and does some strummy leads, and my wife who is very good at appegiating on guitar and 6 string banjo with a 1.0mm pick.
that leaves me and the bass player to put some kind of rhythm to the sound and we do.
He rocks a good 1-5 and does walks and accents. I play lead and a chop/syncopated style with a very heavy pick for clarity.
Those little thin rubbery picks always have irked me because the tone they produce IMO, is weak and unflattering to the instrument. Couple that with a cheap instrument, dead strings, etc and it is just mush.
Using heavier, stiffer picks has made me a much better player. More, tone, control and clarity.