Have you noticed that your iPhone is slower and battery life is worse since installing iOS 14.5.1?
Well, you noticed right.
Earlier this month, benchmark data surfaces that indicated that the iPhone 11 and iPhone 12 series suffered from significant performance issues, so significant that the aging iPhone XR could outperform them in Geekbench and 3DMark tests.
But it seems that this performance issue goes hand-in-hand with a battery drain issue that affects the iPhone 11.
And it's quite a severe dent in battery life.
An iPhone 11 running iOS 14.5 managed almost six hours in the Geekbench battery test carried out by iAppleBytes, but when running iOS 14.5.1, this time was cut by half an hour.
The iPhone XR also saw a drop, but only of about 10 minutes.
The iPhone 7, iPhone 8, and the 2020 iPhone SE saw a slight increase in battery life, but nothing significant.
Given that iOS 14.5.1 contained security fixes for vulnerabilities that are currently being exploited, avoiding the update doesn't seem smart.
So, you're stuck with these problems.
However, a fix is coming in the form of iOS 14.6. Currently in beta, this upcoming update doesn't suffer from these battery and performance issues (at least it doesn't as of the time of writing).
So, it's a case of sitting and waiting for the update to land.