- 14-18 UT trained RA will anyway win any counter battery gun duel so making the causalities very lopsided.
<puts artillery corps-belt on>
Well... they might. Thing to remember is that modern artillery is quite a different beast to WW1 artillery. Modern guns are individually more capable than what was available then (lighter, more mobile, more accurate) and fire better ammunition (longer-ranged, more effective, and again more accurate). It also makes use of equipment that simply was not available then (radios, fire control gear, location equipment, etc). Doctrine has evolved to match those capabilities.
With respect to the counter-battery duel, there are two components - conducting counter-battery fire, and avoiding it.
When conducting it, gunners with modern training won't be any better off than their counterparts. They're still using sound and flash ranging to locate targets, carrying out paper calculations to aim the guns, using runners to communicate that information to the gun positions, and then firing WW1 shells from WW1 weapons. I don't see how any of that could be meaningfully improved simply by different training.
When avoiding it, the main difference would be "shoot and scoot" tactics - that is, displace immediately after completing a fire mission to avoid counter-battery fire. That may have an effect, but it might not be much of one. Consider:
WW1 guns firing WW1 shells with WW1 fire-control and targeting are less effective than their modern equivalents, so they must fire more shells to achieve the same effects. This takes longer, meaning they must remain in place longer to fire them and giving the enemy longer to respond. Once they begin displacing, this takes longer too - the guns are heavier and more awkward, they're usually using horses or trucks that are (by modern standards) weak and underpowered, and there's more of everything to move across terrain that is more difficult, so they can travel a shorter distance in the same time. The enemy will be firing more guns at them and less accurately, so the counter-battery fire will be spread over a larger area. An enemy who is sufficiently quick to respond might still catch them before they left the area.
Even once they've successfully dodged counter-battery fire, the disruption isn't over. I'm assuming they have pre-surveyed positions available to displace to which allow them to cover their assigned areas, but it will still take time to get the guns set up there and surveyed in so they can fire accurately. Then you have to establish communications again - tell your headquarters and FOs where you've gone, so that calls for fire can get to you and you can receive supplies of ammo and food, tell your neighbours so they don't get alarmed by sudden loud noises, etc etc. In any event, the gun battery is out of action for a while even if the enemy fire hits nothing but mud. And again, none of this process will speed up simply with different training.
So yes, modern training might make a difference in the counter-battery duel. But it might not be a huge one, and I doubt it would produce "very lopsided" casualty rates.
And part of what makes it possible for the ammunition-hungry fully automatic weapons to not run out of ammo as quickly is that assault rifle rounds are lighter so a soldier can carry more.
And also that the supplies are being moved by all-terrain motorised transports such as lorries. Resupplies of first-line ammo are often carried out quickly, thanks to radios and motorisation, and in quantities that are not practical in WW1. The standard WW1 supply line, lest we forget, was taking ammo off a train, moving it to a forward distribution point by horse-drawn cart, moving it further forward via pack mules, and then often grabbing a bunch of soldiers to carry it the last mile or so.