If you are ADHD or autistic and really want to do presents, you can. All the people I know who have a diagnosis manage it. Treatment of ADHD isn't purely 'get a diagnosis, get drugs'. There's also an element of giving a shit about how your behaviour affects those around you that you care about.
If you are ADHD or autistic you want to make those around you happy, just like any one else. You understand it's important to get it right. You know it's important.
If you can't be arsed to get it right for a big 0 birthday, you just don't give a shit about that person. There are lots of people who you can ask for help if you, yourself struggle. It's an active choice not to.
You are NOT helping people like my son who HAS a diagnosis. He's 11. He's perfectly capable of understanding the concept of getting someone a nice present and managing to sort this out.
So somehow this 'undiagnosed' middle aged man who should know better and has a hyper amazing job is somehow being outwitted by an eleven year old boy with an ADHD diagnosis. Odd isn't it?
Or you just are writing off anyone autistic or ADHD as fucking useless whilst enabling fuckers to have an excuse to be totally feckless and thoughtless. That's not actually supporting and helping someone with neurodiversity. And then virtue signalling as if you have a fucking clue and trying to show how much you are enlightened and care about all these poor people with neurodiversity.
It's not being nice or kind.
Hint: ADHD and autism run in families. I may be somewhat personally more bloody aware of this than you...
Men who suddenly get diagnosis in middle age tend to have had a female do all their emotional labour their whole lives previously rather than take responsibility and organise. I note the diagnosis AFTER the wife gets fed up of doing this and divorces him followed by this miraculous life changing epiphany that he can suddenly do things. That's not the ADHD that's the issue... That's the taking others for granted and then no longer being able to do that. Funny that divorce followed by getting his act together - causation and correlation issues in your example are going on here.
Strangely women, who are much more likely to be undiagnosed, and don't get this luxury of being feckless and HAVE to take responsibility and organise and remember birthdays etc. This might that be something to do with the point that they don't have a support human to enable them to be feckless.
If miraculously, millions of women diagnosed with autism and ADHD manage to remember their children's birthdays and manage to buy them the presents they really want, I'm finding it really rather odd how undiagnosed middle aged clever men are getting a free pass to fecklessness.
Sorry but the narrative here is just offensive.
ADHD or no ADHD. A selfish inconsiderate fucker is still a selfish inconsiderate fucker.