honestly, it sounds like your dm was just unpleasant rather than changlings themselves are the problem as you can do this with just a lot of magic.
Yeah, certainly, but that experience stuck with me -and in a very negative way.
At the time, his explanation was that their shape-shifting was an innate ability, so changelings could do it all the time. They didn't need items or material components or anything else; they're a common Eberron species.
Unfortunately, having that negative experience forever colored not only how I view changelings, but also Eberron as a whole. There are a lot of pieces and aspects of the setting which I like (and have borrowed to use in other games). But thinking upon the setting after already feeling a negative way lead me to mentally poke holes in some other things.
For example, how does political intrigue and diplomatic conflict between nations, dragonmark houses, and etc function if you can never be sure that the person you are talking to is actually the person you are talking to?
In my mind, I can't shake the idea that it would be like adding the worst parts of Twitter troll anonymity to in-person day-to-day life.
You're right in saying that similar things can be done with magic. I lean toward the opinion that magic and magic items of that nature should be rarer than they are in contemporary D&D.
Fighting a bog hag in a lair and dealing with glamour as part of the challenge? Cool
A lone treasure chest or oddly placed peace of furniture which turns out to be a mimic? Ok
Never having any confidence that I can trust my perception nor trust any of the in-game information available to me? It was difficult to engage with the game or make meaningful decisions.