I connected our two Nest 3 thermostats to Alexa when we used the Echo for a short time. The linking of accounts was not something I liked at all and even when it worked it was just awkward to ask it to change the temperature and way slower than opening the nest app on my iPhone and doing it.
Hidden therein somewhat lies the problem here. Try echoing

your Echo experiment using HP & Siri.
Of course, the "I can use my iPhone" option will tend to be better in many cases. EXCEPT, mobile devices leave home with you. You reference "our" above. So you are not single, living alone. If your iPhone goes out with you, a good device left back at home can serve the OTHER people there (yes, I understand they could all be outfitted with iPhones too, but that's much more expensive than a HP, Google, Echo, etc).
So, there you summarized a "clunky"(?) application of Alexa that worked but was not streamlined. Now try to do the same with Siri on HP. Can you even replicate the "clunky" option without having to use your phone?
Much of these arguments are not that Alexa/Google/Cortana are (Iron Man) Jarvis capable, just MORE capable and/or seemingly smarter than Siri in many ways. People can easily isolate things they want any of them to do that they don't do... or don't do well. But even there, the question can be what can they do vs. can HP's Siri do that too? Presumably, I'm guessing it would be hard to make such a list and have it end up that Siri does as much as the others, and/or seems as smart as the others in ways these devices are already used.
This is certainly not arguments that Amazon > Apple or Apple is doomed, just a bunch of Apple people- including admitted fans- admitting that this smallish piece of Apple- SIRI- it not as great as we believe it should be by now RELATIVE to other VAs that have popped up since. If the "smarts" in this "smart" speaker were at least as good as the competition, no one could deny that this would be a better product. Instead, a majority(?) seems to tag it as a "not-so-smart, but better-sounding speaker." That's fine but we're accustomed to Apple delivering best... or just covet it.
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Actually large, messy setup is the problem. My wife wants to make 'ugly boxes' disappear, I want (reasonably) good sound, so HomePod it is.
In my actual listening/theater room, I have a much more extensive/expensive/messy setup. But then I mostly just listen to music that I already have.
To each his own. The comparison is towards apples & oranges. One HP is not equivalent to a 5.1 surround sound setup. So where a person wants music only and minimal speakers, it is a fine choice.
My 5.1 setup is mostly hidden but if a "wife" took issue with the relatively small amount of space that kind of setup takes (or just the aesthetics of it), one can make speakers virtually disappear altogether with in-wall speakers. Then, one doesn't even need the smallish space an HP takes up... and NO visible wire either.
Playfully, HP looks like a roll of jumbo toilet paper on it's side, proudly displayed somewhere in the room. Our love for Apple can make our "wife" be OK with that look vs. options that involve buying speakers not branded Apple. However,

TV is still an Apple product too. And "wives" generally do like to watch movies. And movies are generally better in real surround sound instead of faux surround and/or mono+ or stereo-. My setup shows no wires at all, unlike a HP which if prominently & proudly displayed does come with a wired "tail" that is the power cord. 2 HPs would have 2 visible "tails". 5 HPs would have 5 tails.
But again, to each his own. I think the HP looks great. I can easily imagine Apple people (like me) enjoying putting it on display like a piece of fine art if they want to do so. I fully grasp the wife factor too but I wonder if that wife would be as married to only a HP as a speaker for this kind of use vs. Google, Sonos, Echos... especially when price is presented too.