Neither helm or istio are part of the core.
Kubernetes is more than what's in the Kubernetes core GitHub repo, it's the collection of tools that go along with Kubernetes that "average users" expect to just be there. For example, an ingress controller, helm, likely soon cert-manager and external-dns too.
The split out into multiple projects actually makes the landscape harder. Where by people and distributions have to make choices about the set of expected vs set of provided features.
A great example of this I saw was an internal thread here at SUSE (I work on their Kubernetes product) where ingress controllers were being compared. Despite the Ingress data model actually being in the core, features like nginx-ingress-controllers ability to do arbitrary TCP and UDP ports on the same external-IP were being seen as a reason to choose that controller over some of the others. I can't argue the feature is useless, because it's not - it's very useful - but it's a great example of how things can very easily become conflated, even for people who should know better! A feature being part of the core just means it's part of a minimal Kubernetes deployment, while a complete Kubernetes deployment includes much more than core.
Are you asserting that any modern production environment that takes less than 2 months to set up is bound to cause problems? Or the whole company/startup/project?
If the former, I'd say there are many tech startups who would disagree, or at the very least, point out that it doesn't matter because they'd cease to exist during those 2 months without an MVP in production.
The time intensive phase during the first Kubernetes deployment is changing the mindset of the engineering team and everyone involved in IT.
Kubernetes IMHO is pretty much like moving from college into work life and adapting to the fact that requirements for a decent adult life are very much different from a college life.
One might reasonably expect "everything" to include traditional deployment methods that require no changing of mindsets (not that that's likely a factor in my nascent startup example).
Think being a startup where deployments most likely will be manual and undocumented, upgrading to an initial automation using some scripting, transitioning to CI/CD, etc.
So from various experiences at companies of all sizes I would actually support such a broad claim, since companies are basically transitioning all the time through new phases to greener pastures. That of course assumes that the company values constant improvements and uses an iterative process for growth and change.
If you have an existing production which works well after years of improvement and stabilization, with people with a lot of expertise on it, you won't get that in 2 months, not the stability and quality nor the ability to troubleshoot it.
Startups start from scratch, don't have big workloads, also there isn't so much pressure to have a high quality service from day one because you don't have that much people consuming your services.
It's certainly in line with technical new hire productivity "ramp up" time estimates (typically 3 months?), which I would guess are a similar (if individual) case of change-of-mindset.
While it's true that some of our customers have an army of consultants, the vast majority of our customers don't use consulting at all or that only use it very infrequently. If you don't want a lot of customization, have the right amount of people and the right people and realistic expectations you don't need consulting at all.
When people want to get a highly customized experience (often, for the wrong reasons), or want to get in production after 2 months, when their people have no experience in kubernetes and didn't do adequate testing (load, fault-tolerance, etc) it will give lot of problems. But that's the case for everything, not only for kubernetes
In my opinion (mine, not Red Hat's) getting someone to deploy it with you the first time, showing how it's done and why things are done, and after that and do a workshop explaining the basic concepts has great value, saves a lot of time and isn't expensive.