For context, I have never worked for or with google, and don't use their products much other than search. So I don't have much emotional connection to the company. My comments were more motivated by a kind of concern.
My perception is that Google split into a number of focussed business units when they became Alphabet, with the Google component being execution focussed and the more speculative stuff spun out into other group companies like deepmind, waymo, etc. That's why the Google unit stopped doing nice incubator projects that we were all excited about.
From what I've seen, this cash cow execution business unit has been fairly effective - in particular they've done a good job of entering the cloud market space producing a differentiated product that is penetrating their target customers. They have not been able to compete with Microsofts excelent and deeply embedded IT sales capability, so they've done well to go after people with big problems that other vendors more civillian offerings are not so great for. They are currently the first choice platform for AI training for instance.
I'd contrast this to Facebook who seem to be trying to become a deep tech VR hardware vendor in the same business unit as their cash cow entertainemet and advertising business which has confused investors and probably distracted their focus.
We can see that Google has innovated. For instance, a lot of Tela's stock price is based on the idea that they are going to run autonomous taxis, and instead of owning cars we will just hail a Tesla when we need one. Telsa does not run autonomous taxis, but you can ride a Google Waymo taxi today in Pheonix, and they are running autonmous trucks which is a big industry Tesla aren't even attempting yet. They are doing a lot in medicine and medical devices. This seems a lot more diversified and innovative than other companies - it's just not as visible to the HN community as an RSS reader or some other internet thing we care about.
We can also say that... on the AI thing, I think it's very early days. Microsoft have a shakey looking deal with the first mover, but Alphabet and Facebook have the advantage of actually using AI extensively in their real buisnesses and may be able to deliver product market fit better. Time will tell.
On the stocks front, I agree with your overall thesis - I think it's harder for these conglomerates to grow than a new company just because they are already giants in their niche and even adding a new niche generates less growth in percentage terms than for a smaller company starting from a lower number. I just wouldn't actually bet against google as much as I would some of the others.