There is so much yet not known or controllable in microbiology, it does worry me that the prevailing attitude is so confident with the little that is known and doable. Its alarmist and uncertain, but so is the foresight that significantly increasing ghgs through the whole atmosphere is too dangerous, or filling the sea with more plastic waste than there are fish left in it is not worth the price and risks. Hopefuly culture is on the verge of accepting these concerns have had rational basis. It needn't result in the end of modernity, but in the appreciation and protection of some older things.
Evolution takes a long time. It's not totally unfair to describe humans as that amoeba, now approaching the nightmare scenario of consuming almost everything on earth.
To illustrate with the previous example, insects evolve resistance to the chemical countermeasures that plants evolve. But give those countermeasures a GM kick, and insects won't be able to keep up. I'm sure eventually they would evolve something, but there could still be a huge crash in their population before that happens.
That sort of thing has happened before though. Oxygen was originally a pollutant that caused the extinction of most species on the planet. This is sometimes called the Oxygen Holocaust (more commonly, the Great Oxidation Event https://en.wikipedia.org/wiki/Great_Oxidation_Event).
That oxidation event represents one major collapse on an ancient scale, but did not owe to a species over-predating others, which Im considering here as a more pervasive risk for species 'dynamics' than pollution/poisoning.
I find no firm answer to these concerns. We dont know that species genetic information has not evolved to avoid over-competitiveness, configurations that could be broken by non-evolved modifications, mass reproductions and releases into the system. Its not a matter which can be settled by current insights, so its somewhat plausibly disguarded as fear and uncertainty. But it might even be the case that what genetics may naturally evolve are naturally confined to modest competitiveness by a property of the yet mysterious steps which enable life to evolve - because we don't even know in what circumstance life evolves. Plenty of theories but no one has ever observed life assembling and evolving from lifelessness, or even modelled a viable sequence illustrating it, and not from lacking of trying for the great achievement and accolades that would bring. Its such an amazing scientific subject, the developed science is amazing too but not nearly so much as its subject matter - biological complexity and remaining mysteries. Its worth treating with special care and humility of some kind.
The presumptive outlook is that all of the simple and complex evolutionary processes are in sum and product - assuredly mundane, stochastic, resilient to any accidental discord which could be caused by humans bodging their evolved configurations and then non-competitively reproducing trillions of carriers and spreading and maintaining them across the globe with no means to ever recall the version. That's GM agriculture described 'on an equal footing' with the products of natural history.