To be honest, if your DM isn't riffing on the sheet notes, they should be, IMHO.

One OG sign it's well past due: players gettin' lazy w/ "low-level" challenges, letting IRL statblock fluency drive in-game assumptions, etc. Resistances, key abilities, tendencies, phobias, et al, should all be up for grabs if the party, or any members thereof, haven't personally encountered said creature before in that biome, region, local area, season, and/or time of day. Who knows what effects to only those parameters brings about in that species? Besides, playing "by the book" doesn't require playing "from the book". 🖖🏼

Time to finesse those goblins, kobolds, infernal geese, ~(normal~ ~geese,~ ~better~ ~name)~ slimes/jellies, mud crabs, the lot!