Agree, every platform has it's distinctive look & feel and as a user I expect that my apps follow this for 100%. Recently I checked out Flutter, with the 1.0 release i thought it's worth to play around with it. The first thing i did, was installing their demo app on my iPhone they showed on the release event. Within seconds I noticed that there was something wrong. They tried hard to reimplement the bounce effect during scrolling on iOS, but it just didn't feel 100% right.
I totally understand, that not every user out there has this sharp eye for things like that and that there is definitely a business value going cross platform, but this is not something I would be proud as a developer. It's the cheap root for the developer ending up in a cheap experience for their users. Share your business logic between platforms if appropriate, theme it for your CI if needed, but do the UI as expected.