This is not a purely technical objective you're trying to do here, what you want to be accomplished also requires social actions. It's not like you can make a BIP and then all altcoin stakeholders drop what they're doing and exclusively use BTC, many of them have their own reasons why they need/want to use Monero/Zcash// or others, which people are never going to come to a consensus to with just new designs and technology alone. I fail to see how this is a problem in the first place.
I am not a technical expert, but I know a lot of people who would drop their holding of many altcoins and get back into Bitcoin if sidechains would enable better privacy.All BIP proposals happened just like that, some people wrote a code, people tested it and see how it works, bugs got fixes, miners and nodes saw potential for improvements and profit and they accepted it.
As far as I'm concerned, I don't see any problem (or particularly care) with whether people want to use bitcoin or not or which particular altcoin they use, it's not like the act of using one is a threat to bitcoin's existence.
I really don't understand what are you talking about...Bitcoin dominance is dropping for years and it was even below 40% recently so money is obviously going away in different distractions and stupid projects, so it's obviously affecting Bitcoin.
