Hey UG community, so I've been playing my guitar lately, which I haven't done in a long time and I've been playing around with some weird tunings. I was just wondering if it would be worth it to leave my guitar in D standard all the time and just capo 2nd for most of the music I play? 'cause I love the D standard tuning, but I don't want to have to re-tune every song
Watch out for tuning and intonation problems, especially up the neck, if you do that.
Is this an acoustic or electric guitar? Does it have a cutaway?

An 14 fret acoustic guitar becomes a "12 fret guitar" tuned down to D standard. (12 fret acoustics are made also). You will run out of neck sooner.

Acoustic guitar bodies have a tuned resonant frequency. Some sound better than others when tuned down

My advice would be , tune down if you like, but try a one step heavier gauge string set the first time you change strings. Dreadnaughts tend to be boomy and maybe even a little bit sloppy in the bass, so a higher overall tension string set will help out with that.

Lighter gauge strings tuned down, don't always have enough energy to drive an acoustic soundboard correctly, and sometimes have a sloppy response.

Other than that, keeping a guitar tuned D to D standard is an old trick to help out baritone singers who just can't hit the G above middle C, correctly. (E-1 3rd fret).

Paul McCartney used a D to D tuning for "Yesterday". The descending vocal arpeggio, "Day, ay, ay, ay" begins on F above middle C.
Sure. If your range isn't limited, that sounds like the easiest and cheapest solution. Make sure you have the strings you like for D-standard and you're perfect.
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Why not? It's very easily reversed and if it makes it more convenient, go ahead, you don't need the permission of strangers.