There's about 200 million active domains currently. That's about 66% of all businesses worldwide of which there are around 300 million. Around 100 to 150 million have active webpages
Where do you get stats on this info? Not refuting your claims but it's interesting data. I would've thought a wider gap in all biz to active websites since some countries run nearly all their biz on whatsapp/telegram/wechat.
What a homebrewed solution lacks in coverage it excels in indexing and serving a small slice of the internet really really well.
Almost anyone can put together a basic search engine in a few thousand lines of code, it's just not very hard to make a program that will index a few million documents better than Confluence.
Then, between that first ansatz and a working scalable internet search engine, you have a pile of interesting problems touching every aspect of computer science and computer hardware and networking, enough so that hundreds of people will have gotten PhDs in narrow sub-problems of those problems you'll be facing.
It's great because you can just tackle the stuff you feel comfortable approaching and leave the rest for later.