Well, the DMG certainly changed it.
There are 27 regular named magic weapons in the DMG, 2 cursed and 11 Staffs.
2 Cursed weapons have a bonus
13 Regular ones do
14 Do not
5 Staffs do
6 Staffs do not
In total 20 named weapons have a bonus and 20 do not.
There are 15 special armours and 3 cursed ones.
5 have a bonus
10 do not
Of the cursed ones 1 has a bonus and the other 2 do not.
In total 6 named armours have a bonus and 12 do not.
Well, let's take this in context.
The Oathbow is +0 against most targets, but it is Advantage (i.e. +4 or +5 equivalent to hit and +3D6 damage) against it's sworn foe. It is typically way more powerful than even a +3 Bow and if it ignored piercing resistance, it would be nuts.
The Dancing Sword does not have a bonus, but it gives a +0 to hit extra attack per round. It's pure bonus damage.
The point is that some of these weapons might not have a bonus to hit, but they are still more powerful than ones that do.
And Staves are glorified Wands. The ones that are also magical weapons are supposed to be the exception instead of the rule.
Did you include the Rod of Lordly Might? It's the only rod that functions as a magic weapon. Personally, I would not include Rods or Staves in the "magic weapon" department at all. They are mostly magical spell carriers with charges that sometimes function as a weapon.