"Apart from all the many succesful products, everything they did was a failure" is an empty statement which can be applied to any company. So yes, you can say that about Alphabet. You can also mention that they have a market cap of $1.8 trillion and are the fourth most valuable company in the world.
Their successful products are vertically-integrated to provide a walled "convenient" experience to users. You use an Android smartphone to open their browser, searching for stuff and viewing ads, using Maps to find the ___location of businesses appearing in the ads. The rest of their contributions are welcome side-effects that have enabled running that software and hardware infrastructure.
Meta doesn't really belong in there, not much vertical integration there, it's very horizontal with instagram, whatsapp, facebook, threads (lol!) serving similar and sometimes overlapping audiences. They don't really provide a service beyond social media (unless you count the OSS / free software they release for devs)
Yep, the parent comment is the part of the iceberg "above the surface", but there is also a bunch of influential stuff "below the surface", like their AI research, and things like colossus, borg, bigtable, mapreduce, and a few others.
Google acquired YouTube, they didn't make it, just like Android. At the time Google had Google Video which was terrible in comparison, and although Google was already the most used general purpose search engine, YouTube was so much better that it had already become the standard for publishing and/or searching videos.
They also acquired Android, Docs, Sheets, Slides, and many of the precursors of Maps & Ads.
There's value in scale. The YouTube founders themselves said they couldn't have grown YouTube without help from Google infrastructure and other business functions. In the mid-00s people were just figuring out how to run an Internet business with billions of daily users; this is a service now externalized through Cloud providers (including Google), but back then "not falling over when you got Slashdotted" was a key competency that Google had but many of the thousands of other Internet startups did not.
With all these other video services adding frequent commercial breaks, consuming youtube premium is looking better every day. I absolutely hate-hate-hate commercials while I'm engrossed in a movie, may as well just watch short content on youtube premium.
Nothing apart from search, ads, maps, Gmail, Chrome and Android was a huge success. They essentially created their own monocultural ecosystem.
Most of everything else was a short-lived fad. Plus, Wave, Reader, Chat and Glass, to mention a few.