I want to play audio from my Mac over WiFi speakers without having to install a bunch of apps
AirPlay Speakers

The easiest experience is to get AirPlay 2 compatible speakers and you have zero app, native OS support, works everywhere experience. 


https://www.imore.com/best-airplay-2-speakers
https://www.apple.com/ios/home/accessories/#section-speaker


The airplay page and marketing logo explain why this takes away the need for any apps, and is strictly controlled to make your experience better. 


https://www.apple.com/airplay/




I get you might consider this smart home, but for sound the setup and reliability are amazing and for me worth the cost. 

AirPlay Adapter

Alternatively, you can get a cheap AirPlay adapter and connect it to existing speakers. This gives you all the benefits of AirPlay without high cost of AirPlay speakers. You can connect to any existing speakers you have that take an aux input. The adapter connects to your WiFi network at home, and allows any Apple device in the house to stream music to your speakers.


Example adapter


Bluetooth Adapter

Also available without AirPlay - a dumb setup is going to be a $35 or less Bluetooth receiver to powered analog input speakers. 


Logitech Bluetooth Audio Adapter for Bluetooth Streaming 
whichever studio monitors your heart desires