Home Assistant is currently working hard on assistants. I’ve not used it much yet but their text to speech offers so much more than any of the larger companies in just customisation alone, plus it all runs locally.
I have Google Home devices all over but they currently mostly act as a dumb speaker and I just get HA to do all of the heavy lifting. The most Google does is set timers and even that just goes into HA for most of the processing.
It’s not hugely complicated but instead of me having to ask an assistant everything, I let HA tell me everything through various speakers based on the state of sensors around the house at appropriate times.
When I wake up in the morning and go downstairs it’ll detect my presence, and if it’s a work day it’ll inform me of weather, traffic (as well as a suggested time to aim to leave by) and a basic schedule of my day, then it’ll stick some music on.
As it gets closer to the time to leave it’ll chime up again telling me I have x minutes left to get ready, but only if it detects me in a room so I definitely hear it.
All that is controlled by HA automatically and isn’t something you’d ever get from any of the big players, because they don’t have the sort of information and stats that HA does.
If I set a timer in Google Home then it’ll become available to HA through it’s integration and I’ll pop up a timer bar on some of the displays I have dotted around so I can track the time left without having to talk to the assistant, and as any timer gets close to expiring then it’ll even show a message on the TV saying which timer is about to activate.
There’s a few smaller things that just make life a bit easier too, like turning speakers off in rooms that aren’t active, or integrating my dumb doorbell into HA using an RF receiver so I can automate doorbell presses.