A warranty usually only covers mechanical breakdown or defects.
Home contents insurance doesn't cover mechanical breakdown or defects, but will cover things like fire and theft - which are NOT covered under the warranty.
Your insurance will cover things like theft, fire, flood, water damage, vandalism, etc.(whatever the policy states). It can also, if you get it, pay you enough to replace the items, not a payment for the devalued object ("replacement insurance" is not expensive).
Warranties do not cover fire damage or theft. Only insurance covers these things.
Home insurance does not cover things that stop working on their own (because they are worn out or defective). Only warranties cover these things.
They are for completely different, unrelated, non-overlapping situations.
It is debatable whether there is ever any point in getting an extended warranty. However, there is as much point in getting an extended warranty if you have insurance as there would be if you did not have insurance.
There is a point in getting insurance, whether or not you have a warranty, and it is the same point, whether or not you have a warranty.
The point of insurance is to cover fire and theft, which are not covered by warranties.
The point of warranties is to cover breakdowns, which are not covered by insurance.