We should stop thinking in terms of "tech companies" and think of them in terms of "companies that use tech with a high degree of success". Ultimately any company that makes money is not a tech company because pure technology on its own does not make a business. Also, with the right incentives and management it is possible, although hard, for legacy companies to start using tech better to compete.
As an example, pencils are an excellent technology for writing. (Petroski's "The Pencil" and "The Evolution of Useful Things" are great reads on how much innovation it takes to make something mundane.) But Faber-Castell is definitely not a tech company. Similarly, ~100 years ago, electricity was novel. Fortunes were made starting and investing in electricity and electrical-adjacent companies. Now it's mundane.
Dealing with novel technology requires different skills. Both for the specific technology involved and for wrangling things that are less well understood and keep changing. A good example is the IT department and what they are and aren't responsible for. The breakroom toaster? Nope. The breakroom wifi? Yup. The breakroom TV? Well, that depends.
For me the useful dividing line for "tech company" is where novel, volatile technology is at the heart of their business and vital to their success. That doesn't last. And indeed, the markets have been too generous about pretending certain things are tech companies. Most notably, WeWork, but I'm sure here folks here can name plenty more.