Every manager should be sympathetic to their team and try to make a reasonably accommodating environment. However, it’s still up to the employee to take ownership and be accountable for getting things done. You can’t reasonably expect managers to constantly micromanage employees to extract work from them, nor can we expect companies to create perfectly distraction-free environments. At some point, it’s the employee’s responsibility to manage their own output.
It’s not just the employer who suffers when a team member is unable to complete tasks. The rest of the team has to step up and fill in the missing pieces or constantly watch over the person who can’t get things done. Eventually you start losing talent because your good employees are tired of doing a job and a half while some other employees are only delivering half of their work, and everyone suffers.
Employment is increasingly a 1-2 year stint where workers are swapped in frequently and you need to get value out of them before they leave. But it really screws over people who are not known factors or who might need adjustments.
And that's okay. Startups are a little over-romanticized anyway.
You might be surprised by the hyper-focus abilities of folks with ADHD.
Keep in mind that your perception is skewed by selection bias — you probably already know many productive coworkers that never told you they have ADHD.
ADHD symptoms are a multidimensional spectrum [citation needed], and so-called normal people lie somewhere on that spectrum. Making affordances for folks with ADHD is a win for everyone. For example: write meeting notes and assign action items, use a bug tracker, ask people if the process works for them.