But is there any better alternative? Say for example, that at some point you have two semi-independent goals - you need to complete both A and B to proceed towards your primary goal, but it does not matter in what order you do them. Let's assume A and B are "equally" hard. Say you do A first ... spend a lot of time on it - it is pretty hard and time-consuming, but your party gains quite a bit of XP, levels and gear. Then you do B, but if it does not scale, it will be ... well, very, very easy compared to A, because of everything you have gained while doing A - and if it is not a real challenge, it will be a disappointment to some.
I would prefer to have some limited scaling in situations like that.
Too much scaling is even worse, however. If I reach a high level and return to a typical starting area - say, a rat-infested basement, I don't want to see duraluminum-plated, fire-breathing rats. Likewise, if I wander into a dragon lair at the beginning I should get killed, not have to fight a tiny, wimpy dragon whelp.
The right level of scaling to me means to have major NPCs, their spells, skills, pets, henchmen, gear and treasure scale a bit .. within a limited range - in D&D terms something like "NPC X will be set to level 13-17 depending on average party level when you first encounter him". To me, that is reasonable, and keeps the game challenging, without making the scaling silly.