In today's world, perhaps, but it must have taken vast amounts of time until the first bacteria covered the planet. If abiogenesis were a frequent event on the early earth, there should have been plenty of space for more than one lifeform to survive before life became ubiquitous. And of course it's possible, but it shouldn't be the default assumption either.

Sure, that's a plausible account. However, they would only compete if they appeared in a pretty small geographical area. That still leaves it as being a relatively singular event. Maybe much more than once in a few billion years, but still much rarer than many seem to assume.

I would also note that we don't really know of any mechanism that would require millions of years for chemical reactions, or any equivalent of the theory of evolution that would work for hypothetical complex organic substances. Not to say that either is impossible!