I don't think Pixels let you keep all the functionality when you unlock the bootloader. Am I wrong?
You might be thinking of SafetyNet. I'm not sure if there are any reliable ways to get root without tripping SafetyNet, but last I knew you could - on a Pixel - flash a different ROM and then relock the bootloader, and you'd be fine. Things may have changed in the last few years though.
You still fail SafetyNet if you do that.
What apps are actually enforcing SafetyNet?
I wonder if would it be possible for something like εxodus to detect this when they scan an app. I'd love to see a SafetyNet flag in their scan reports.
Snapchat, Netflix, Pokemon Go, Super Mario Run, Android Pay, McDonald's, and most bank apps immediately come to mind.
Most of those make sense but why McDonalds?
None of them make sense. Remember that if it were really about security, then phones vulnerable to Dirty Pipe wouldn't pass, but they do. It's just about control.
"Coupon fraud"
It was always my banking apps that caused me problems.
You retain whatever functionality you want when you unlock the bootloader, or relock it after flashing.
Apps can choose to not service you if they detect modifications though.
You're being obtuse. An application choosing not to service you definitely counts as losing functionality.
When the hardware was painstakingly designed so that I can't tell those applications "no modifications here", that's very much a manufacturer and OS problem.
You're not wrong. Android Pay will stop working, and so will a bunch of third-party apps.
You can use Magisk + Zygisk/DenyList to get these apps working on a rooted device.
The trick Magisk modules can use to hide the unlocked bootloader only works as long as Google still supports legacy devices that didn't do hardware attestation of the bootloader being locked. As soon as enough time passes that they flip that switch on their end, that will totally break forever.
Also, even today, a few apps aren't fooled by that solution. Try the McDonald's app for example.
If Google decides to corner everyone it will only empower them to put energy into non-google ecosystems. It would be a big mistake IMHO for google to cut this off.
Pixels have their own issues. For example, Google at some point decided giving users HDMI-out was cannibalizing their Chromecast sales and haven't offered it on their phones since. They tend not to play nice with combo 3.5mm/charging adapters, and often have bizarre hardware and software issues that only crop up a few months after launch. Their new SoC is essentially a rebadged Exynos, and as a consequence it has trash GPU drivers that gimp gaming console emulation to an astonishing degree. Pixel users can't crop the screen to hide the camera cutout so I hope you enjoy watching videos with the world's biggest dead pixel on one side of the screen.