Solution to my issue was to download the ESO installer, "install" the game but change the install location to the folder where the game is already installed.
When I did that, the problem was instantly solved and the "play" button was avaialble again.
Without trying to start something, what do you mean by that? I'm pretty sure I'm just not getting what you said, so...what do you mean by that sentence?
Are you talking about more options with the launcher itself, like it not being tiny on a screen with a high resolution? Because that is annoying, yes ^^