cmad1977
Hero
I've run and played in games that went all the way to 20th, personally I didn't experience an issue. YMMV of course, but high level play felt suitably heroic to our group. We were fighting dragons and creatures of legend, handling region (if not necessarily world shaking*) threats.
When we did fight low-level monsters, we fought mobs with dozens if not hundreds of opponents. When our wizard called down tactical nukes (aka Meteor Storm) on our enemies it felt pretty cool. As a DM I just went a little over the top with some encounters and turned the dial up to 11 ... and then celebrated with my players when they stomped on multiple level 20+ monsters.
Throw in a handful of legendary magical items and we felt suitably heroic. Maybe not superhero powerful but that's just a matter of expectations and game feel.
*That's kind of a personal preference. How many times can you avert the end of the world?
In the latter stages of ToD(where players got to 16th or so) I thought to myself:
Self:”is this scenario too metal?”
Other self: “No. In fact... it needs more metal”
Self: “OK! More fire giant ballista!”
At high levels I think you need to turn it to 11 and have fun with epic scenarios.