Your thinking about materials is a bit flawed there.

You have biodegradable bags that can hold water for days (5+year old tech). Same for weather-proof packaging. Nowdays that is not the issue, it took (only) a couple of years but companies have developed good alternatives.

Even those cardboard ice cream tubs from like 10+ years ago can hold water for months (had it outside & left it when I noticed how it didn't let the water go yet - it was the less waxed outside of the packaging that gave out first).

Three is a huge difference between dissolving in water immediately or after months - or even never: eg cellulose ("wood") doesn't dissolve in water as such, but it's eaten by a huge number of various bacteria (which ofc doesn't happen within hours of using the straw).

Cardboard straws getting soggy is just a design flaw of that specific product that (it seems?) gets sold anyway, bcs consumers don't demand better & rather blame the gov doing good than the bar/restaurant/store not giving two fucks (or just bcs profit) & ordering actually viable stuff.

Another example - several decades ago the paper industry developed those little transparent/seethrough windows on envelopes from celuloze (~paper) just bcs they just wanted to ditch the plastics industry. And nobody noticed.