If you’re using an iPhone 6s or newer, you’re golden. Anything older? Not so much.
While that may be disappointing if you fall into that category, it’s for the best. Owning an older device and then having a software update make it slower, with battery life likely impacted, is no fun. And at that point there isn’t a great deal that can be done about it, either. There are definitely worse places to be stuck than on iOS 12.x, too. That update added improvements to performance on older devices. Clearly Apple didn’t believe it could pull that trick again with iOS 13.