Spoiler: No, we're bloody well not.
I hear this an awful lot. Any discussion where someone is talking about the traits they have that are 'on the spectrum' (whether it's the spectrum of ADHD, ASD or something else) tends to end with one of the people in the conversation saying "we're all on a spectrum!", usually with a nervous laugh. It always frustrates me, because it has never once come from someone else who I know or suspect actually is experiencing ADHD or ASD. When I hear it from someone who is plainly neurotypical, it suggests that they don't understand the difference between an occasional misstep and a lifelong impairment... which really shouldn't be that hard to figure out.
When people say that we're all on a spectrum, I expect that they're thinking about a spectrum of human behaviours across the whole population. For the 'social communication' spectrum it might look something like this:
And to an extent that's true. However, when we talk about the "autistic spectrum", we're not talking about a whole-population spectrum with an "autistic end". We're talking about the spectrum within autism itself, which is a spectrum of impairment.
Lots of people have worse-than average social skills, but manage to get by without their social awkwardness impacting on their friendships, earning potential or mental health in any particular way. It is only once social communication problems are a burden that an autism diagnosis begins to enter the picture.
A more accurate diagram of the social communication spectrum would look like this:
We can talk about the spectrum of human social communication skills, sure. But when people with ASCs talk about being "on the spectrum", we're not talking about the whole three-colour spread. We're talking about this bit:
The ASD spectrum is a spectrum of impairment. It is the degree to which (for example) poor social communication skills affect the person's ability to function within society.
Claiming that we're "all on a spectrum" ignores the fact that being on the spectrum of impairment is by definition far harder to live with than being placed anywhere else on the whole-population spectrum. "I feel shy sometimes" (red 'no impairment' zone) is not the same as "My voice actually shuts down for hours after a stranger addresses me" (blue 'impairment' zone). The autism spectrum isn't about how good or bad your skills are, it's about the degree to which your functioning is impaired by those gaps in your innate skills.
To give the ADHD version, "everyone loses things sometimes" is not the same as "I frequently upset or inconvenience myself or others by losing important paperwork, even if I've made a conscious effort to keep it safe at some point".