I got a Wii U in 2014, but I only used the tv for Splatoon and local multiplayer. Do the Wii U Gamepad and Switch handheld mode count as HD?

Wii U Gamepad, no. It's 854x480.

The Switch screen is 720p, so that is HD, though as with Wii U/PS3/360, not every game on it runs in native HD.

I was playing DS, ALL the time during the late 2000's. So HD wasn't even on my mind.

then I bought a PS3 out of hype sometime in 2009. Hated it. Bought a Wii Christmas 2009 and basically I haven't touched HD since. I bought a 3DS and that's what I play now.

I plan on buying a Switch this year, and this is when I will "officially" transition to HD.

So 2018 would be my answer.

hd on pc propably before 2005? I don't really know. I just remember a 1280*1024 resolution.
1680x1050 on pc around 2007.
hd on tv (old used tv) in 2008, used it only for wii and hated it, looked worse than tube tv.
fullhd on pc and tv in 2011.
not really interested in 4k.
I don't remember ever having that "wow" effect in those screens.

2013 when I moved house and decided it was easier to buy a new TV than break several family member's backs lugging my gigantic CRT up the many uneven steps leading to my new house. In retrospect I wish I'd just compensated them for any potential injury since there was nothing like it for playing pre-HD games.

HD didn't impress me, it sometimes looks pretty nice and maybe I couldn't go back but the lack of a significant improvement reinforced my already held belief that I should just skip 4K and wait for 8K, 12K whatever comes next.

Actually I just remembered I did buy an HD TV in 2007 (can't remember if it was 720 or 1080) but returned it the same day when I was utterly unimpressed with it and that was before I got my 38 inch or so CRT, I was just using a 14 inch Sony TV from the 80s with about 9 channel buttons (no remote) one speaker on the side for mono sound (but it had a headphone port for stereo) had RF and SCART but I didn't consider HD a worthwhile upgrade to that relic.