Not all adventures are replete with magic weapons…
For example, if you look at
this excellent archivist work of compiling all magic items from Dungeon of the Mad Mage (a levels 5-20 adventure), you’ll see very few weapons. Most of the weapons are longswords, which is fine if you use that, and disappointing if you don’t… there are a few others, but with a strong emphasis on "few". Armors and shields are similarly infrequent. Moreover, whatever weapons and armors are present drop fairly late (assuming players go down the levels in sequential order, which they probably should, even though portals could take them much deeper in a jiffy!)…
The quest has a fair amount of items overall, though many of them are not that strong (except towards the end…). Also, this list does not include the fairly generous amount of spellbooks that can be gotten in many parts of the adventure. This is nice for Wizards as spellbooks are not that frequent as loot (in other adventures)…
Overall, if the DM does not allow crafting, purchasing or exchanging magic items, I could see DotMM being a bit difficult (though I haven’t played it myself, so can’t tell for sure).