I wouldn’t say it’s a waste of athleticism or speed, and certainly not defense. Slight imperfections in Ath and Spd won’t kill you in press/zone, and stamina is not normally an issue, unless you’re also running fastbreak, or are trying to go with a 8-9 man lineup. Athleticism (especially for frontcourt) and speed (especially for guards) still matter on defense; but if you can always have some elite defenders on the floor, you can also find ways to use guys with less than optimal defense who have elite skills elsewhere (rebounding, scoring, distributing). You can utilize skills, and worry less about defensive flaws.
With zone, you are trying to win by suppressing the other teams FG%. You get a small rebounding penalty, so I try to make rebounding a little bigger priority. And you don’t foul as much. On the flip side, it’s harder to produce turnovers, which is the big reason I use HCP. I generally spend about half the practice minutes on the press as on offense and zone, since you’re only using it for roughly 1/3 of a possession.