It's not about your kid going to a Spanish class once a week, and the objection isn't that doing that isn't enriching for your kid.
The problem is over the holidays when all your kid's friends have been sent to camps and summer schools (mostly as a form of holiday childcare for working parents presumably) or taken away on holiday, leaving your kid with nobody to play with. It presumably varies a lot but it's a real thing in our and our childrens' lives. The summer holidays should be filled with friends and play, not spent at home with your parents because nobody's available.
I still prefer my kid I'm camp or summer school over the kid on Netflix or Steam or whatsapp whole day. Or over me forcing them away from the above after which they still don't go play outside with friends, because friends watch anime or play video game.
The problem is over the holidays when all your kid's friends have been sent to camps and summer schools (mostly as a form of holiday childcare for working parents presumably) or taken away on holiday, leaving your kid with nobody to play with. It presumably varies a lot but it's a real thing in our and our childrens' lives. The summer holidays should be filled with friends and play, not spent at home with your parents because nobody's available.