Heh, let's see you get your donkey to jog for 8 hours.
But, really? Now we're saying that the Sword Coast is so pacified that a lone traveler could walk from Waterdeep to Baldur's Gate regularly?
I think you're vastly misinterpreting what people have been saying.
Nobody is saying that the roads are going to be completely safe. And I'm pretty sure that a lot of travel is done in groups or in armed caravans. But the fact that there is actually a road called the Trade Way proves that there is travel.
Plus, considering the way D&D works, anyone who decided to travel even relatively short distances and didn't die right away could easily earn a few levels with doing so--even if they're in a group and have to split XP--so by the time someone decides to actually make that long trek alone, they might be somewhere in the 3rd-to-5th level.
Just in case you decide to reply with "And now you're saying everyone is high level in the Realms!" or "it's not supported by the books!" well... there's plenty of precedent, since 3x had those NPC classes like commoner and noble, and in 5e, they could have the Sidekick classes. So why not? Because the NPC statblocks don't reflect that? Well, change 'em! Say the average peasant has 8 hp, two stats at 12, and is proficient in one of Dex, Con, or Wis saves. No biggie there.
Is that what's seriously being suggested here? PC's must be the absolutely most unlucky people in the world.
Probably, since I doubt that the DM is rolling for random encounters for every single NPC in the world.
Oh, and apparently the church of Waukeen can employ thousands of workers for decades (what it takes to build a road that would go from Paris to Athens or Toronto to Miami) and then maintain that road. Despite there being absolutely no mention of it anywhere in any of the source material. What there IS mention of in the source material is how many freaking monsters, hostile humanoids and various other threats there are to any traveler on the Trade Way. Again, there was a DRAGON living a couple of miles from Phandelin.
FIrst, how old is the world, and how old is the church? They could very well have built that road centuries ago and have been maintaining it ever since. And they very likely don't do it alone. There are
plenty of gods and churches in the Realms who would find maintaining roads and protecting travelers to be important, and probably
many more kingdoms/baronies/counties/etc. who would have a vested interest in doing so. Do you really think that anyone is saying that one church is doing everything on its own?
(And yes, read up on Waukeen. Her clerics often work as bodyguards specifically for traveling merchants.)
I doubt that dragon actually kills every single person who dares to leave Phandelin just for giggles. And remember what I said about people leaving offerings for the forest spirits? What if it's the same with the dragon, and they toss a coin in a ravine or something, and the dragon accepts that as enough of a bribe to not go out of its way to kill the travelers. Unless it was already planning on doing so because it was hungry.