Yes, but note that carriers will do all of the above. Use their licensed 'sub-6g' spectrum where traditional cell networks operate; make use of unlicensed spectrum for Passpoint Wi-Fi, use (licensed) mmWave spectrum.

Depending on the venue, they're likely to do a mix of whatever is most cost effective. But more spectrum, if usable by the handsets people actually have in their pockets is helpful.

Wi-Fi barely works in a hotel, how is it going to work in a stadium?

Last time I was at a stadium (4 months ago), it seemed to work pretty ok. I suspect that it's setup and maintained by a mobile carrier rather than whoever does IT for hotels is helpful. Most stadiums have a lot of days with minimal activity where you can do an intensive install and tweak session, but hotels are hard to take out of service, so kind of works is good enough.