Batts from Walmart should be fine if, like any other battery, they are maintained properly. Are they as good as Trojans?...maybe not, might have slightly shorter lifespan, especially if doing a lot of boondocking, but the differences would be slight other than that.
When a dealer says that Walmart's batteries are junk, in my book, they're just trying to upsell you on batteries. Your batteries may very well have been bad...but buying them from Walmart had nothing to do with it. Having a shorted wire that would intermittently drain/short them would.
Jim
2005 Pace Arrow 36D
Very Understanding Wife
1 Boxer 😞
3 Maine Coon cats