"Competition is good because it leads to cheaper prices for consumers", doesn't really work since it neglects the union of the state and monopolies to artificially charge higher prices for items of the same - even worse quality; while hindering competition that has the potential to change the status quo.
I mean—the US is trying to prevent the world from cooperating with China, Russia and other major economies because they know that they are incapable of competing due to their decades-long crusade of neoliberalism. Another example is the fossil fuel industry stalling for time against the wave of the renewable energy era; or the automobile industry lobbying against efficient public transportation.
The point is that the major neoliberal powers don't want competition to exist; they just want rent-seeking sectors that can earn them a treasure trove of money as fast as possible.
I don't think that we disagree. Because, for the reasons that you have provided, competition will produce almost-indestructible monopolies as a natural consequence, and those monopolies have a tendency to use their extensive power to destroy and buy out potential competitors and seek for quick, easy ways to accumulate wealth; notably, through rentier capitalism.
This is literally what's happening right now; at least, in the US.