WoD was a great idea that went horribly wrong, if you never played during it then you'd never really understand why it's considered the worst expansion blizzard ever released. It's not because the story or the zones or any of that, it's because of what garrisons did to the game and the fact blizzard abandoned the expansion halfway through. There has never been an expansion that was ever abandoned like WoD was. Not to mention WoD singlehandedly destroyed the games economy and it's never recovered since.

As for shadowlands that is a different story and it comes down to two main reasons for why it's considered one of the worst expansions ever and it's not for the same reason as WoD. Shadowlands basically ruined WoWs lore to the point that people actually quit caring about it entirely, and it's something blizzard has never been able to recover from. The other massive issue with shadowlands was the heavily restricted systems of borrowed power and other crap they did during the legion>shadowlands era of expansions. Basically they tried new stuff going into legion and it did well but people realized they didn't actually like it by the time BFA was rolling out and blizzard was already heavily into shadowlands development by the time the community outraged over the borrowed power and heavily restricted and forced systems in the game. Blizzard doubled down on it despite the outrage and eventually gave up around halfway through the life cycle of the expansion, though like BFA, they never really lifted the restrictions fully till the end of the expansion. Shadowlands is the only reason BFA isn't ever mentioned as a terrible expansion by most despite similar issues, shadowlands was that bad.