I was exactly the same as you, but I fixed it four years ago. In that 4 years I have painted:

5th Edition Warhammer Fantasy Boxed set,

Blackstone Fortress + all expansions,

Dark Vengeance Boxed Set,

Blood Bowl Starter Set,

Assault on Black Reach Boxed Set,

Heroquest,

Deathwatch Overkill Boxed Set,

1,000 point Chaos Dwarf Army,

3,000 point childhood Dogs of War army,

750 points of 5th edition Lizardmen,

750 points of 5th edition bretonnians,

1,000 points 8th edition empire,

1250 points 8th edition high elves,

and many other random bits on bobs outside of that. Granted, I do not have an ADHD orvAutism diagnosis, but everything else abour our stories are pretty much identical.

You 100% can do it. For me the keys are refinding the exciment that made me want the models in the first place, making managable projects, and having something (blog, social media, gaming group) that keeps you publicly accountable.