I almost never see ads on my phone. Of course I use paid apps for most things, and deliberately shun ad-heavy apps. That's my preference.
I don't have any voice assistant devices, also through choice. I was given a Home Mini when I bought my phone through a promotion: I actually contacted the vendor and asked them not to include it, but that seemed to be too complicated for their systems to cope with. I gave it away to a local sports club to use as a raffle prize. As
@ocnbrze says there are plenty of wireless speakers if that's what you want, and if you want a voice search device as things currently stand you'll have to put up with the tracking (of course some of them have also been recording more than they let on, and you have to take on trust that the companies have actually addressed that, but that's also your choice).
You could of course create "burner" accounts for individual devices, so that they can't connect up the data, e.g. an Amazon account only used for Alexa, and a different one for actual shopping, a Google account only for Google Home and separate from your phone. If you use a computer rather than a phone there are a wider and deeper range of techniques available (on this laptop any Google or Facebook site I open is placed in a sandboxed tab with no communication with the rest of my browsing, cookie data etc. They can track what I do on their site, but I see no reason they should have access to anything else).
