In my opinion, net worth is just a kind of useful "pulse" metric to keep an eye on how you're doing overall.
First, to address the "net worth" when buying a house, as mentioned in a comment, other than transaction costs, you should not have taken a huge hit when buying. The house should be valued close to the overall purchase price.
Net worth should include adding up all assets, such as what the house (and cars) would sell for, any 401k, etc, and subtracting any liabilities, the mortgage and other debts. At the moment of buying a house, you gain debt but you also gain the house as an asset. They roughly cancel each other out. I doubt the transaction costs exceeded $200k!
When you dive deeper into personal finance, depending on your goals, other values may become more important, like the total amount of assets you can and do invest so that they generate their own returns.