Sure, the picnics were fun at times. And things seemed more wholesome and innocent back then. But wan't that true in the world at large? Most folks were innocent of many realities of the world like genocides in foreign countries, babies dying of starvation, girls and women being raped with cultural permission, etc. And now we have news 24/7 and the world is a different place. Every generation says the same thing. But now we have more knowledge and more choices. Many have more freedoms than they did decades ago.
BUT let's not forget that many jw wives were/are being beaten at home with no choice to leave. Many jw children were/are being molested in their own homes by men in their "happy" jw congregations. I have family members in their 50s who still talk of the molestation they suffered. They remember the picnics and gatherings as opportunities to hookup/escape with other teens who were miserable and wanted out so badly but had no place to turn. There are multiple Generations of exjw teens who were frustrated and hopeless who have been lovingly counseled and assisted disfellowshipped in groups by the elders. So not only were they harmed growing up, they lost their family connections and were tossed to the curb. Today more just lead double lives and don't tell. But they have more choices when they leave and many are faders.
Any activity in which you're invested 100%, when everyone around you constantly reassures you that you are Right and Wonderful and so is your future...sure, that's gonna feel good. But being a jw is living in LaLaLand. It's not reality. For many the reality of being a jw was hell.
Once you know reality, those "fun" jw memories come with a price.