There's certainly something interesting about taking multiple generations, but it also feels kinda wrong to attribute greater meaning to something because you dragged it out or intentionally scoped the project too big.
Maybe if the project served a greater purpose and couldn't possibly be built in a shorter time, then it would mean more. But a cathedral? What's wrong with a modest church or two?
Sure, the same amount of stone could be used to construct several smaller churches. The US congress could also just rent a conference room at a nearby hotel if they chose. The Eiffel tower could supply iron for several kilometres of rail track, or maybe a small boat.
But building something extravagantly big has a signaling value all of its own: "see the glory of <whatever it is we constructed this for> and how much resources they command". You don't build a cathedral because it's more practical than a normal church for holding services and stuff, you build a cathedral to express the power of your religion and impress it on others.