I’m gonna go way out on a limb here and assume that people wearing leisurely attire while engaged in leisure activities are doing so because they are engaged in leisure activities.
Believe it or not, baseball caps and the bills on them, as well as sunglasses, are intended to protect the face and eyes from direct sunlight, not to transform a Jew into a non-Jew. Likewise, jeans/cargo pants and sneakers are important if one is engaged in an activity that will damage or wear at finer, thinner, more formal wear. T-shirts are infinitely more effective at wicking away sweat and letting in air than a Shabbos shirt. People are dressing smart, not “goyishe.”
It appears to me that you are applying your own preconceived sinister intentions to people who may be guilty only of engaging in an outdoor activity.