I more or less agree, assuming I understand what you mean about losing the original techniques. If the techniques are teaching valuable (reusable) principles, then they serve a purpose, even if they aren't directly useful. There are techniques in the formal NGA curriculum ("Classical" techniques) that I would not encourage someone to try to learn to use for combat, sport, or defense. I find them useful tools for exploring, learning, and developing some of the principles. To me, they serve the same purpose as drills, though we call them "techniques".My opinion is that, while this is true, you also shouldn't lose the original techniques.
This is an opinion that has started many an argument in the TKD forums.
But if a technique isn't directly useful, and doesn't help develop principles or teach movement useful in the aforementioned "grey area", then they can go. I'd even be okay with someone deciding to drop some of the NGA techniques I've referred to (and still call what they do NGA), so long as they're covering those principles elsewhere.