Mods are busy trying to collate the issues, and honestly, threads such as this are little help. I understand your frustration but can assure you the new UI was tested by volunteers and was working fine before release.
The Devs are working tirelessly to patch the current issues. As with previous major iGP updates there is a degree of chaos. This is not an excuse, unfortunately it's just the way of things for a small independent studio rolling out a major update worldwide to many thousands of players.
Jack posted this on the volunteer Discord server in the last hour...
it's so hard to explain this to anyone
but what is going on is the servers
this is really low-level server stuff, it has nothing to do with all the front-end update
that's why it's impacting all the race results etc. and the GUI works fine
while all the inevitable "didn't you test this" stuff is being said, what is broken isn't anything we changed, ironically
it's the stuff that stayed exactly the same as it was before and which was running like clockwork for months
Please be patient. By all means report bugs and issues that you are experiencing but expecting the game to be reverted to a previous version is unlikely to met with a civilised response. If it's any consolation I have experienced a number of major updates over the years and the Devs usually sort everything out more quickly than I ever thought they would.