Flutter - Software Conception

A softwere can defer from another like a humen from an alien. A website may simply serve as a business card, showing 5 pages, it can be a blog software, a shopsystem, and even more sophisticated, a B2B trading app.

Flutter doesn't yet have a wide range of open source solutions for high availability apps respectively usecases, which would work out of the box.

Here is a list of complex modules, which can be a part of software:

ECMS - Enterprice Content Management System
DAM - Digital Asset Management
DWH - Data Warehouse
eCommerce - Online Shop System 
EMM - eMail Marketiing solution 

Any of those systems can be part of a software but may also need interfaces to other software, like a DWH to an Online Shop and of course usually companies choose the system with the least development cost, which still can produce a high  workload, especially with less experienced developers.

So generally its a good advice to have somebody develop a solution, who can serve most of your demanded usecases.