Uncomplicated ADHD is ADHD without any co-occurring mental health, developmental or physical condition that would change how it is assessed or treated.
It's a research and clinical shorthand. Many trials recruit people with uncomplicated ADHD so the results aren't affected by other conditions.
Adults who come for an ADHD assessment often also have, or have had, something else: anxiety, depression, sleep problems, dyslexia, autistic traits or a history of substance use. The assessment has to look at how each condition affects the others.
If your ADHD is uncomplicated, the medication route tends to be simpler. If it isn't, that is normal, and it is the reason a full assessment matters more than a screener. A screener looks at one set of traits. An assessment looks at you.