Really? Have been an xbmc/spmc user for years now got a new device with recent Kodi and default skin (I think) and it might be 'somewhat' clunky but I definitely wouldn't call it 'extremely clunky and slow'. I consider it just fine and not that much of a difference with spmc of a couple of years old. What are you runing it on?
I wouldn't call it clunky and slow, it is just meant to be used from a tv. It's like saying steam big picture mode is clunky if you use it with mouse and keyboard. Kodi has a good api, although there are no good web interfaces yet, I have been also contemplating trying to build a cli around it
It depends what hardware you are running Kodi on. I was running OpenElec on a raspberry pi, it was pretty much unusable for me. When I opened Kodi, the scan for new media would take ages, and often not work at all. Now I had a dedicated Windows 10 HTPC with an SSD, and the experience is night and day versus the rpi.
Yeah, I usually give up and go to Netflix or Plex.
Having to click in to each link, then in again to the stream, then load it up, then back out, and that process again for the next episode. Just one example but there are lots of things like that.