so really those relatively mild "relatable" symptoms can't be said to have a "significant negative impact"?

A "negative impact" can and is as simple as "causes undue stress"

For example, the OP meme happens to me multiple times a day, daily. I notice it and it actively stresses me out and annoys me and worsens my mood when it happens. Sure, it's not making me kill myself or ruining my work or life prospects, but it's a low level sign for sure. It's literally one of the big things my psych focused on during the diagnosis process

Another example is OCD, it can cause stress and anxiety without the person being unable to function, or even do quite well in work and life.