Suggested

Windows software?

I does have a Browser version. Please use it on a 64bit machine and Firefox for better experience.
Pre-load the viewer watching another race in spectate tab.

It's not a flaw it's a workaround to preload the viewer and racetrack data if your internet connection can't cope with the requirements. I know it's not always, or at all, possible to get the internet connection you wish to have but that's the bane of all online games.

If that's right then something's wrong with your setup or ISP because the viewer loads several times faster even on mobile without LTE, which maxes out at about a third of the downlink of your line.

I wouldn't mind a client but there are quite a lot of players that won't try a game on PC if they have to install something first. Plus it'll be a lot of work just for a client that isn't more than a browser that keeps its cache until the next game update and you still need to maintain the 2 Apps for mobile and also better the browser game for other platforms (Macs, Pads (if the Apps still don't scale to the screen properly and give them the full game), Linux and for work, school and public computers.

You aren't cleaning your cache every time nor running Chrome on Private mode, are you?
If you want fast load, stop doing that :)