I don't think euphoria is inherently a problem, is unethical, or should be considered wrong to desire.
But that's theoretical because I don't think it exists as an entity on its own through these drugs (and with benzos which is all I can speak to I don't think it exists at all).
If you could be at work being productive, interacting with your colleagues, then with your family, at the supermarket, acting ethically, would be there be anything wrong with feeling euphoric at the same time?
It's everything that comes with it in reality that is the problem.
I think we conflate the current level of technology with the ethics of a situation.
The "drugs are bad" message because of their health effects gets mixed in with the idea that they are bad because they make you feel good. Them making you feel good does not seem like their vice to me.
If the tech were better, I don't see the issue with enhancing experiences. People could argue like they do about so many things that something is only worthwhile if you put in the effort, that reading is better than watching a movie, that reading a paper book is better than an audiobook, blah blah blah. Taking a drug is the easy way out. Well if it is easy *and* safe (again hypothetically), I don't see the problem.
We've associated drug dependence and bad health effects with the "easy way out" (which it really isn't given the former) because of the limitations of the technology which seem more like an accident of history than anything else. Leo Sternbach discovered benzodiazepines instead of something that keeps working indefinitely and doesn't cause tachyphylaxis.
In other areas of medicine like primary care and cardiology, doctors are practically begging patients to take statins, as an example, despite that being an easy way to prevent deaths from CVD. They are easy. They work to some extent whether or not you change your lifestyle. And they don't stop working. In fact, over time, they stabilize plaques and continue to improve health. Actual health. Not just symptoms. To me it just seems like an accident of fate and history and biology that nervous system disorders drugs are the ones that have such limitations.