Sorry to hear that you are frustrated. The warning prior to the upgrade has been put in place to let you know that if you use an application/plugin/theme/language pack in the marketplace and that there is an upgrade (or not) for it so that you don't encounter a broken community when you upgrade. If you have a completely custom theme, the warning in place is for you to check the theme because we don't know what is happening, so we just want to give community administrators a heads up prior to them pulling the trigger.
I'm afraid, this a choice to run these addons/customizations and, unfortunately, keeping them up to date is a requirement if you want to upgrade your community. If it is causing frustration, you may wish to limit the customizations that you have on your community so that things are more unmodified/default and can be upgraded without worry. There is the "Easy Mode" theme editor where you can change colors on the theme but keep templates the same, so you don't have to worry about a custom theme upgrade.
Alternatively, this is not a security release so you're more than welcome to take your time in upgrading to ensure that you get your customizations working. Releases on our end will be monthly so perhaps when we start announcing betas, it would be a good time to start preparing yourself for an upgrade, if you choose to continue running customizations. It is also worth noting that December and January releases will be more maintenance/bug fix related so it may allow you to pace these upgrades.