Google isn’t exactly known for supporting unsuccessful products for very long. It’s been 4 years since the initial release of YouTube Gaming and the company is already getting rid of it. To be honest, it’s probably for the better.
Most of the people who are in theory should be Youtube gaming. If you want to keep using some of the features which are specifically aimed for gamers, then you have to check YouTube’s Gaming Hub. This section is here to compensate for the discontinuing YouTube Gaming.
The exact date of shutting down Youtube gaming is May 30th, 2019. Google announced the end of support of the product in September of last year, so the discontinuation isn’t that surprising. If you want to continue viewing gaming content, just use the standard YouTube app.