That isn't true. A good scout has more influence on the game than a good arty does. This is evident because the scouting effect is continual, whereas the arty effect is sporadic. Moreover, mutlple angles can be covered by a scout whereas arty will only hit in one place.
While it's less true that the armour mechanic is stronger - broken heavies aside like 279e, - they still have greater ability to influence due to dishing out more dpm at the same time as being hull down, so it can't be said it is less critical either.
The conclusion about bots is a separate issue. Bots don't do more than regular players can. The reason arty bots go for arty is arty has fewer places it can safely go on the map. It's a a backline vehicle by design, which means it has less risk from bad coding. And your coding choices are limited so easier to do... and bots are all about doing things cheaply for the return. More complicated choices means more costs, which means your returns are less, making them less economical and so less viable.
As for having limited ability, not sure how that's relevant. People with limited ability play every class of tank. And I doubt your conclusion is supported. I'm not aware there's been any evidence that shows people "with less ability" 'play arty more.' And even if there was, not sure what it would achieve. Do you think removing a class of tanks entirely would cause those with less ability to disappear? (And is there any justification for that, or is anything WG would be trying to achieve?) No, they would just go on to whichever class suits them more... probably the blue clickers.