Earlier quoted context omitted.
Glass is literally molten sand. It will break down just like the rock breaks down. It's not toxic or hazardous, except when it's freshly shattered, but these super sharp edges weather relatively quickly, after which they aren't any sharper than natural found rock. This not to say that we should just don't care and throw away glass anywhere we want, but it's really not a huge deal, unless you hate seeing glass pebbles…
This all hinges on what you mean by “relatively fast”. If glass is being shattered and ends up being a hazard for years, this is much worse than a goopy old discarded plastic bottle, regardless of the perceived ugliness of the latter.
No, over time the plastic bottle will weather into cell-scale microplastic particles and play indefinite havoc with local wildlife. Glass will not.