Yes, it is. I mean, GrapheneOS is the gold standard for privacy&security, but even stock Pixel is a good step up. Think of it like this: on stock Pixel, only Google is tracking you, not Google + Samsung, or Google + Xiaomi. Just Google. It's guaranteed to be a step up from all other Android phones, stock or not.
Technically it is just better than the worst possible case, which is two companies or more spying on you instead of one that was already spying on you. It is still bad but better than the worst case.
Wait since when a monopoly is preferable to a duopoly? As far as I'm concerned if I can't have 0 companies to spy on me I'd rather have them all fight each others in the data space...
In this case they don't fight, they exploit your data in different ways and if one of the exploiters isn't arsed to keep your data secure then everyone gets it and it's not just corporate actors profiting from you but more harmful actors including scammers using your data.