Abstractly on Flutter

Flutter framework is the only framework that has come closer to satisfying this adage: "Write once, Deploy anywhere"

Flutter apps could be literally deployed on all the major platforms that any business wants to that includes Web, Mobile(iOS/AOS), Desktop (masOS, Windows, Linux), which covers all the major platforms and there's really no need of writing platform specific code as Flutter framework does it under the hood for you plus there are a variety of plugins written by a thriving community that makes it even easier to develop apps.

basically, with Flutter you have everything you need to develop apps without worrying about maintaining multiple platform codebases which is the main reason[read: lower costs] why companies opt for cross-platform frameworks in the first place. 

listing out the pros&cons on a very high level:

Pros:

• good documentation
• apps are fast since for ex mobile apps are not reliant on the Javascript bridge for communicating with the native layer
• open sourced

Caveats:

• Flutter apps aren't native, so still there are some build/profiling time & app size tradeoffs that we have to make, which is inevitable
• Flutter is a fairly new one and hence nurturing & developing the community would take a bit of time which limits us to the available tools & libraries

if you're planning to go with a cross-platform framework, I'm wondering why would anyone want to develop a frontend app on any platform using any other framework when Flutter could do pull that with ease beating almost all the other cross-platform/hybrid framework out there.

It's the decision maker in an organisation who decides which framework to use and if the decision maker isn't adopting & upgrading themselves, they'll surely be less informed about the differences between the frameworks and are sure to go with the sub-optimal one, which always happens with most organisations out there.

this is nothing against other frameworks(RN, Ionic, etc) but a fact that you know why its better to choose Flutter over others, if not for other reasons, at least you could rationalise yourself that it is not necessary for a popular thing to be the best.

as of today, its not totally wrong to choose React Native but if you're starting from scratch and your team has people whose expertise is not just with javascript, then there's no reason why you shouldn't choose Flutter.

like my earlier post on React Native, I've rewritten the same app using Flutter and have open sourced it for your perusal

note: I re-wrote this app in just about couple hours