I concur. Just moving over from RingCentral which does have ical integration, I find this a step backward in this regard.
I also find it hard to believe that you think that Macs are not mainstream enough in the business world or would not warrant the development time to implement a simple link or plugin.
I'm having the same problem and find it frustrating that even simple support for generating an .ics file ist still missing from GoToMeeting.
It would would make things a lot easier for everyone outside the Outlook and Google ecosystems and shouldn't be rocket science to implement.