D&D, especially in the current edition, seems focused on large 1-13 level campaign adventures. I'm not inherently against starting at Level 1 (especially for new players), but when you've been playing for years, Level 1 adventures take on a sameness: goblin ambushes, lesser undead in the cemetery, rats in the tavern basement, etc. Unfortunately, this design paradigm means that some players (and DMs) get bored before the campaign gets around to "the good stuff."
Starting at Lv.1 & climbing the ladder over & over? That's never bored me.
Where I get bored is when that climb is focused solely on one campaign goal/telling ONE story - such as {nearly} every adventure by WotC here in 5e. I don't
want to spend all of my time/my characters entire run on 1 goal. I want a variety of adventures. Different things at different Lvs most of who's only connection to each other is that this particular group of adventurers did
xy&z.
And now & then? Play a long one story campaign.
Take CoS for instance. People LOVE this adventure! But it's exactly what bores me as a player. From the time it starts (wether that's lv.1 or lv.3) you have
ONE goal. Beat the vampire in the castle up on the cliff & escape his little kingdom.
Even newbies who've never played D&D or heard of this adventure figure this out almost immediately - because it's not a secret.
Great! Let's go on vampire hunt!
So what do you
do lv after lv after lv? Week after week, for months (maybe around a year) of real time? You trek back & forth across this little kingdom full of every horror movie trope you can list, gathering the quest items,
having the same flavor of play. When all you
really want to do is hop in the black coach & go explore the damn castle.
But you can't. Not even if you'd began with all the items. Because you started at Lv.1. Or lv.3. And you need to lv way up in order to have a decent chance of success.
You know what's even worse here? As you run back & forth you're not actually getting to explore anything related to the characters you rolled up. Everything you do is in service to completing this one adventure.
But wait, things often get worse.... See, getting to "the good stuff" here? The actual vampire hunt? Starting from lv1/lv3 it all takes so long that 1) some of the characters won't survive the trek, 2) a TPK is completely possible, 3) Real Life can easily derail the whole thing.
So you've spent all that time not actually playing the part of the adventure you really wanted to....
Grrr.
As a DM? Very similar thoughts on 5e adventures (and many PF APs), but not as bad. I don't want to run the same thing for seemingly forever. I want to run a variety. And I want to run some stuff tailored to the characters.
Merely having multiple chapters/books in an adventure =/= actual variety (usually).
And yet the classic module this is all inspired by? I6: Ravenloft from the 1e days? An adventure I love as both DM & player?
Same plot & story.
"For 6-8 characters of lvs 5-7"*.
Pretty much starts off going to the castle.
Explore the haunted castle, learn the "story", collect the McGuffins from throughout, & defeat the vampire.
You can accomplish this in a handful of sessions vs spending a year of your life not getting on with it.
It was a one shot story that presumed your characters had prior adventures & would have future adventures.
*AD&D had a way different assumption of party size. Either lots of players, multiple characters per player, npc hirelings, or some combo.
*Each class had a different xp chart. We always assumed the low end of these lv suggestions was whatever the slowest advancing character in your party should be at.
And vampires etc sucked XP out of characters, actually dropping your lvs until you died! To do this adventure you needed either that larger party size or just more lvs.