Neither the assessed value for property taxes, nor the market value of the home has anything to do with the cost to rebuild it if it is destroyed.
You're right, you don't insure the land.
The cost to rebuild your home is likely to exceed the property tax assessed value and, in many parts of the country these days may be less that what you can sell it for.
Use the following Replacement Cost calculator to determine how much to insure your home for and see how close it comes to the agent's estimate. I have used this for my home and have found it to be comprehensive and reasonably accurate. Not far off from what my insurance company estimates. Insurance companies use similar calculators.
https://costtobuild.net/
There is also a garage calculator if you have a detached garage building.