I've run CoS twice (two games simultaneously)... and the only potential issue that I saw with the "Starting at Level 1" thing was the party being sent to Madam Eva immediately upon arriving in the valley. I know why the campaign does that-- because that's exactly what happens in the original I6... but I do think that is the one thing that contributes to how
@Stormdale feels. The party is told at level 3 "The issue is with Strahd, go find these objects to deal with him!" and yet even if they somehow manage to get all the objects at Level 3 they still probably would need/want to "level up" before going after the vampire. So there definitely is this sense of needing to just ignore the "Big Bad" and elephant in the room while the party becomes powerful enough to actually eventually do something about it.
And this is why I'm pretty sure that if I was ever to run the campaign (and I'd certainly love to, as it is my favorite of all the 5E adventure paths by a large margin)... Madam Eva and her card reading would not happen till way, way later in the campaign. Give the players several months of game time being stuck in this dreary land, dealing with all the issues of Kresk and Vallaki and being harassed by Count von Zarovich in all manner of irritating ways (because he's bored and just sees the party as a new group of playthings.) Really put the screws to them to make them WANT to escape the Baratok Valley. And only then... once they've decided they finally want to get out... introduce Madam Eva and the potential solution to their escape.
Now all that being said... I also do agree that even this has the one potential hiccup in that we are asking/hoping the party to decide to want to leave the valley as the ultimate conclusion of the campaign, when the characters have nothing concrete to return home
to. They may have built their characters with a backstory of something to go back home to... but that's just a tell, not show (and is the issue with starting the CoS campaign at levels 1 or 3.) And this is why entering Ravenloft at level 5 or 7 has a bit of an advantage, in that these characters have had countless hours of playtime in their home setting
first-- probably a lot of stories and connections having been built there--
and then they get pulled out and stranded in Barovia. Thus they now have more of an urge to want to go home because they've actually played everything that they have waiting for them at home.
But of course... if you do that, then you run the risk of the players revolting that their stories back home have now been put on hold while they are stuck in the Mists... and then you run the risk of them just rushing through everything to get to the end, thereby losing everything that's cool about the full CoS experience. The same exact issue many players of Tomb of Annihilation had, when the time crunch of the Death Curse prohibited much more exploration of Chult.
In the end, to run the game as well as possible it all requires a careful balancing act on the part of the DM to find that adventuring sweet spot for their players. The downside for most tables of course being that from the sounds of a lot of comments here on the boards, many DMs don't want to actually work that hard at the balancing act, they want to just plug and play (and then they get annoyed that the adventure doesn't work for them.)