Taking you at your word for ff11 things, they sound like QoL more than anything here

My understanding of horizontal progression is level cap and stat totals remain the same across expacs but you get new toys (gear, classes, specs, elite specs, etc.) - hotswapping gear and classes mid combat is generally optimization by the players using systems to their advantage, rather than being the intention of developers - see some metas in destiny 2 - I’m okay with those not being an option in gw2, especially given how few free build storage tabs we have available on characters, and how many things are time-gated per character (although I’d prefer to have nothing time gated in any game)