This is just my experience as an adult with little music background. I tried guitar and it was not beginner friendly for a few reasons:
Notes appear multiple places on the fretboard, which means chords have tons of forms. This leads into my next point of knowing what to play and where to play it.
For reading music (I know you say just read tabs but tabs have their own issues) there are several notation systems that all get crammed together to make sight reading extra difficult. For any given note, in addition to the pitch and duration from the standard musical notation, there may be instructions for which string to fret, which finger on the right hand to use, and which position to be in (how far down the fretboard your where hand is).
Bar chords. I really hit a wall with these and the awful contortions expected of me to produce these.
Counterpoint or music in two parts. Having trouble remembering where a note is as a beginner or keeping rhythm? How about we add a few more than will be fretted differently depending on what comes before or after and that have a different duration? Now move only some of your fingers so you can let one line ring out while playing together from the other line.
You may say that these aren’t beginner topics, but they’re all covered in the first book I ever learned from that started with how to hold a guitar and notes in the first position.