Well, Article I, Section 8 also says that Congress shall have power to “coin money.”
We coin very little money today, and virtually everybody agrees that “coining” money doesn’t limit the government from printing paper money and issuing the other forms of money that the term has expanded to. Some people do in fact consider any form of non-metal-based money to be unconstitutional. Those people are considered cranks.
Mostly all that says is we are not now and never have been consistent in how we apply change over time to the words of the Constitution.
The problem for the OP is that the internet is not in any way a modern version of the Post Office. Even if anyone granted that dubious premise (and could actually explain what the internet as public utility could possibly mean), all that would mean is that the government can create its own internet, not that they could ban use of the current internet, or compel people other than federal employees at work to only use theirs, anymore than the government can keep people for using the form of money known as cryptocurrency.