(a) The web is a failure
and
(b) Chrome monopoly is the best outcome for the web.
OK, obviously the web is great, I'm using it right now, and it hosts millions of useful websites, so why is it a failure?
Consider the simple act of buying something. To make a purchase on the web, I have to type in a 16 digit credit card number, 3 digit CRC number, expiry date, name and address. Every single time. After 30 years of the web, nobody has figured out a way to make this securer or simpler. Well, no, I'm sure many have figured out a way, but nobody has implemented it.
By contrast, on my phone, I can buy with a simple fingerprint check. Apple provides that service, I find it valuable, and the firms in Apple's walled garden of apps find it valuable too.
Why is payment easy on iPhone? Because Apple, as monopoly provider of that walled garden, makes a profit from making it easy.
Why is payment hard on the web? Because there is nobody to make a profit from making it easy.
In short, the web's infrastructure is a massive public good, and like many public goods, in the absence of government coercion it is underprovided.
Web payment is just one example, and I'm sure there are others, but it's an important one. The lack of a decent payment infrastructure leads to pathologies. When paying for content is a hassle, people give away free content and use alternative monetization strategies like advertising - so we get Facebook, "you are the product" and manipulation by algorithms. When paying for items is a hassle, it's easier to just use Amazon who have stored your credit card already - so we get a huge ecommerce monopoly.
If Google effectively owned the web, change would happen faster; users would be more satisfied; web development would get easier instead of being a mass of horrible hacks around 30 years of legacy standards.
There'd still be competition. Apple, Google and Facebook would compete as platforms. That's an oligopoly, but platforms are natural oligopolies - nobody wants 1000 different platforms.
Conclusion: Chrome's dominance is probably efficient.