It doesn't take that long to learn to read sheet music (or tabs especially) and you could treat it like just playing a sequence of notes but you're never going to get far that way. You need to understand why certain notes go together. Some people have done that without theory but you're going to get much further with even some basic theory.

Think of it this way: if you first saw the word "HELLO". You could deconstruct that and remember that there are 11 lines and 1 circle but that's not how you learn to read or write. You learn letters, which are collections of lines. So you learn the concept of "H" and it having a sound and that it is 3 lines. You then learn to put them together and how you can sound out something thats's written and with varying degree (depending on language) take something said and write it down.

Music theory is like that. Sheet music may be a bunch of circles and lines on a sheet but really it's describing keys and usually a chord-progression. Some sheet music will explicitly just list the chords at the top like A, Em, Asus4, etc.

The 12 notes are constructed from harmonics, specifically 2:1 and 3:2. This part is maths. But the frequencies are adjusted slightly in a system called "equal temperament" where the ratio of 2 adjacent notes is the 12th root of 2.

From there you generally play a subset of those notes (often 7). That's called a scale (eg major or minor scale). The chords in that scale can then be identified by a Roman numeral within a key. So the I chord in the C major scale is a C. The IV chord is the F. Depending on the starting note of the scale you'll get sharps (#) and flats (♭) to denote that they are a different pitch. An easy way to remember this is that the white keys represent those whole and half steps with just the white keys (starting from C). As an aside, so does the A minor scale.

Why do I say all this? Because a huge amount of modern music is simply a I-IV-V chord progression within whatever scale you're using. So if you know a little theory, you can choose a key and a chord progression that will inherently sound nice together. There's more to it of course but understanding what a key is, what chords are and what a chord progression is is a pretty good start.