Disclaimer: I work at Google. Opinions my own.
I love Gmail. I've also been an iOS user since day one, and 99% of the time I prefer apps that feel like iOS apps.
I use the Gmail app instead of Mail, even for my personal email, because Gmail has a number of concepts and integrations with other parts of Workspace that don't neatly jibe with the native Mail app. iOS wants to treat labels as folders, which is an approximation. Responding to Calendar events isn't the one-tap, in-place experience it is in Gmail.
The Gmail app also does a few key things a lot better: search is way more sophisticated and reliable; Smart Compose is really brilliant and makes me faster, particularly at knocking out more 'trivial' emails.
The one thing I really miss about iOS mail that Gmail doesn't support is VIP contacts. Gmail has a way of marking emails as 'high priority' and only notifying on those, but its classifier doesn't really match my expectations. As a result, I've just turned off notifications for email. I check it a few times a day. Probably healthier, but esp when I'm waiting for an email from a critical contact, VIP would be awesome.