Here’s the process that used to work (but no longer does as of 2023):

Source a clean iOS 5.1.1 Netflix IPA file from trusted archival websites like the Internet Archive (Archive.org) under legacy iOS app collections.

For many users, these vintage devices still possess excellent battery life and high-quality screens, making them ideal dedicated media players. However, opening the modern App Store on iOS 5.1.1 usually results in compatibility errors.

Reported "Touch and Go"; some accounts may no longer log in [18, 20]

The App Store fails to load entirely due to outdated security certificates (SSL/TLS issues) inherent to iOS 5.

Tap on the Purchased tab at the bottom of the screen.

: Open the App Store on your legacy device and ensure you are logged into that exact same Apple ID.

Scroll through your history to find Netflix and tap the Cloud icon to download it.

Concise conclusion

How to Download and Install Netflix IPA on iOS 5.1.1: A Legacy Device Guide

: Search for this tweak and install it. It removes iOS signature verification checks entirely.

What you are using (iPad 1, iPhone 3GS, etc.)