That statements is so far from true. there are multiple HA systems that. 1. can use multiple "brands" (I assume you meant protocols because "brands" do not matter). wifi, zwave, zigbee, insteon 2. do not require internet: Homeseer, Hubitat, Home Assistant, OpenHAB, Vera, and several others @ @
avitzur ISY is not bad but it is nothing special. It VERY limited in its functionality to pretty basic controls unless you write code yourself or hack-around with an external 'app' systems they connect to which is also not widely used and a 'hack' since ISY is super-duper limited by design. unlike all the ones I mentioned, and others, which have tons of plugins / extensions (some free, some paid) and also have far more built-in functionality than the ISY. I've used many systems. Most ppl on this forum have used 1 system, maybe 2. whatever they use now is "best" and "better than anything" . and they make up BS like the above reasons (which are not even close to tru) bcuz they have no clue what anything else does and in general people feel good when they think they made the "best choice". That choice might be fine for them but to tell you whats "best" for you without having a clue what you want to do, and what other systems can do, is arrogant and does you a disservice.