Mimblewimble doesn't require a fork and is one of multiple solutions that are expected over the next decade.
Since we are only 10 years old in bitcoin, the need for privacy on bitcoin hasn't been a huge concern yet. If it were, the privacy coins would show more users and adoption, while bitcoin can still add sidechain and 2nd layer solutions at any point
I technically agree with this part
But we should take a deeper look and try to understand why privacy is not a big concern (or a concern at all). I have two perspectives on this. First of all, people are using cryptocurrencies for speculation mostly (that's kinda common knowledge but still worth mentioning in this context), and when you are using an exchange for trading, privacy is not what you typically look for or care about (apart from all coins necessarily being in the same league there by definition)
Further, there is a deeper paint to this as the majority of people (and that would be like 99% as I'm inclined to think) don't need the level of privacy that coins like Monero, ZCash, etc offer. These people are quite satisfied with what Bitcoin already has in this department (without any mimblewimble). I could even go so far as to say that a lot people would exchange a little less privacy for a little more profit and without thinking twice at that
It's not a concern because it hasn't affected the price or the status that
bitcoin is the digital gold that funds every altcoin project and ICO.
Sell it and move on if you want. The second privacy becomes an issue, the largest amount of developers in the space will have a timeline for solutions.
It has the largest amount of development and infrastructure throughout this space. Other things die if somehow bitcoin can't be used to fund all of these projects
And as much as I myself support the view that it is altcoins that are taking from Bitcoin and not the other way around, the majority think it is not the case. Besides, you can't say that Bitcoin is actually funding or supporting altcoins as many of them would be perfectly fine without Bitcoin. In fact, I'm strongly inclined to think that they will even do better without it (not all, but definitely some)