I heard from several people that they couldn't dance during the day at the pool because there was no room. Seems like the organizers want to sell as many tickets as possible with little regard for the amount of space.
It's not (only) about space. In my experience it's very hard to make big high quality event.
Yes, I've been to Warsaw fest 10 years ago and to Rostov, but these are exceptions and as soon as Warsaw fest priority became business, the quality went down.
For example rave had many issues with sound, playing same songs, DJs messing up sound, etc.
And I know personally several of invited DJs are professionals. But since DJs were switched up randomly, it seemed noone took or even could take responsibility.
Or let's say salsa is a social dance - how do you find, connect, socialize in big loud hall with 1000 people environment? Dancehouse events had separate chillout/bar environments with comfy seats and lower sound volume, so you could talk. Zeid finds nice venues, it costs a lot more than cheepest hotel in airport area or tourist trap beach town.
Another example - same event with social spaces and garderobes had policy not to bring drinks to the dance floor. Still floor was spilled and people put their stuff everywhere. In big enough events culture degrades, everyone becomes average of the crowd. Or in big events there will always be someone smoking inside. Or right next to entrance.
We've talked about musical selection in other threads, rave was an exception, but as a norm, the larger audience, the more mainstream will be the music. Which means same tracks all the time, and averageness by all criteria. Mediocrity can't be great.
Logistics, lines, congestion, where did I leave my bag, who stole my drink. All these are side effects of party too big.
Also smaller events can adjust to reality much faster. Rostov could switch venues next day, if there was an issue with one. Or organize some other event instead of pool party if weather got bad.
I could go on, but I believe complexity of many things increase with size and to make it work quality goes down.
Then again, in Europe large events have live bands, and smaller ones rarely so. But Berlin marathon has very nice local band, that makes everyone happy.