The lack of a viable alternative is the pretty much definition of monopoly. Just because lots of people use something doesn't mean there is a monopoly.

Def: "the exclusive possession or control of the supply or trade in a commodity or service."

Google has a very nice search engine but I personally fail to see how they control the supply enough to be considered a monopoly. Sure most people use them, but that is by choice. There are viable alternatives.

Standard Oil only maxed out at 90% market share. US Steel only reached 60% of the steel market. There were banks other than JP Morgan. A more nuanced view of monopoly has to do with how much power they can wield in the markets.

And of those which ones had successful antitrust litigation against them? Just Standard Oil I believe.

Microsoft was declared a monopoly when every computer in my school was a Mac. Internet Explorer was considered a monopoly when everyone I knew was running Netscape/Firefox. It's obvious that the US federal government and the EU disagrees with you. You don't have to have 100% control over a market in order to be considered a monopoly.

"Courts do not require a literal monopoly before applying rules for single firm conduct; that term is used as shorthand for a firm with significant and durable market power"