Simplification is just bad. It removes too much that it breaks ability for non-speakers to infer meanings. Complexity of letter shapes is irrelevant to ease of use in computer usage, so it's just a massive loss.
Not sure what you mean by this. Do you mean that it's less convenient for people that don't speak / read Chinese? Why would that be a relevant metric?
You may be missing that character standards have changed over time and that different writing styles (草书，行书) are implicitly simplifications. You can think of latin or Russian cursive as a simplification of the printed letters.
In practice, the phonetic component has been mangled / evolved over time, so simplification doesn't make things more or less difficult for students (be it 5 year old native speakers or 50 year old non native speakers).
Both massive wins
The problem also can also happen when translating from English, if you think about all the surnames that are occupations, or names like "bill" or "lily." Capitalization usually helps disambiguate, but there's title case and all caps and people who never capitalize anything...
The cases where simplification has removed those cues are rare enough that the extra complexity of traditional characters is really not worth it.
I've never heard anyone claim that simplified characters are more difficult to learn, and it just seems false to me.