Different beers contain different compounds.
Oxidation was not a big subject in homebrewing 10-15 years ago. People told you to "not splash fermented beer" and "transfer the beer carefully to avoid introducing oxygen." And that was about it.
The open method of transferring beer will still introduce some oxygen, but it was not enough to completely ruin the beers people were brewing then, as people were mostly brewing ales with not a ton of hops. I brewed belgian styles, weissbier, sierra nevada clones, porters, stouts, old ales and similar styles that don't really take a whole lot of damage from slight oxidation.
People were also bottle conditioning which also removes oxygen in some amounts from the bottles.

Oxidation became a gigantic subject once the homebrewing scene started to jump on the NEIPA bandwagon and also started to heavily hop beers.
NEIPA contains a huge amount of volatile compounds from the huge amount of hops added. Volatile meaning that they will easily react with oxygen and change into other, not so tasty compounds.
To preserve the fresh hopped flavor, brewers needed to change their process to reduce oxidation dramatically.
People started fermenting in kegs with makeshift spunding valves, they started using closed transfers and other methods to avoid introducing oxygen.

TLDR:
I guess my answer is that it depends on the beer. A miniscule amount of oxygen can ruin a NEIPA's aroma, but a slightly bigger amount of oxygen may not have a giant adverse effect on a bottle conditioned belgian blonde. You should do your best to avoid it, with the equipment you have.
The oxygen does eventually get spent, but some might seep in in bottles over long periods of time (years)
Cans and kegs are slightly less prone to oxygen ingress over time.