Experience from "MP" project. When I joined this team, I was the 7-th. Project was conceived as "Start-up", fusing telecom and blockchain technologies. Besides the full-time members there were part-time "experts", so it was almost a small army! Despite of this, development was markedly slow and haven't reached production even after more than year of efforts.
Let's see what the "core team" consisted of:
Still this list lacks some important people: Quality Assurance specialist (or "tester"), Business Analyst, the person who defines and clarifies the tasks - and Frontend developer (UI, web). Some of them joined later.
What is wrong with such setup? Just as the Bible says about Babylon Tower: several people are carrying single brick instead of one person carrying several bricks. Many calls, few responsibility.
Let's go through the list in order.
Project owner is generally out of question. Entity which exists and couldn't be changed. It is good for product owner to have background in IT and play role of manager or BA for example. It wasn't the case though.
Manager. Larger companies generally allocate single project manager for 3-4 projects. There are not always enough work for single manager in single project. Thus it is good for manager to be also BA and QA for example. In this case manager generally neglected to write tasks requirements so later it sometimes was hard to figure out whether they are fulfilled by implementation.
Security Guy. In brief, it was premature state for full-time security specialist. It soon appeared that security issues are overestimated and the fellow was reassigned "to help with backend". Regretfully it wasn't his strongest side. Security too.
IoT specialist and Hardware programmer - why two? because IoT specialist wasn't good in hardware programming. That's bad, he often had nothing specific to do or was assigned tasks for which he was not exactly capable.
UI developer and UX designer who appeared bit later were separate people. Often developer needed to wait for designs for several days, because designer was part-time participant.
To conclude: it feels like the team was assembled faster than understanding of the project evolved. Also it often feels difficult to say farewell to members which appear unneeded. In larger company it is possible to move them to other projects, but it is not the case for start-up.