Whether or not it's a good change is likely mostly subjective. I'm guessing Discord made the switch to be more in line with other mainstream social media platforms, and to reduce confusion.

Personally, I kind of like the old way more. It means there could be 10000 different people with basically the same name. Other than paying for a specific number, there is no issue with a person grabbing a handle and then it not being available to anyone else. Otherwise, eventually, a lot of handles will be used up, maybe even dead, so people have to come up with increasingly creative ways to get a unique handle – or just settle on adding some numbers to the end.

I'd even go a step further myself and remove handles completely. Just use a random unique identifier, like a hash or GUID for the user – which a lot of platforms do under the hood anyway, since you can change your handle in many of them – and use invite codes, QR codes or similar to add friends. We don't need this username / handle rotting that just gets worse over time.