What is the actual, achievable endgame for cryptocurrency?

This sub is particularly defensive whenever people point out the flaws inherent with the current construction of Crypto coins and economies, but one thing i never see get genuinely answered is what does a mass-adoption end state for cryptocurrency actually look like?

As it's currently built, proof of work blockchains are far too slow to have crypto exist as an actual alternative currency, and vendors who have picked up crypto as a sales mechanism until now have either not had much traffic through it or have dropped support altogether.

In it's current state, with the complete lack of regulation that has led to some huge personal losses, rampant scams and the problem of there being no central blockchain that is being adopted, how can it grow out of anything other than a speculative (and highly risky) investment vehicle?

For the record, i'm not shitting on the idea of an alternative currency that could usurp fiat money around the world, but is there a genuinely achievable endgame where crypto can actually become a usable currency that can support even 10% of the transactions that carriers like Visa can support?

Is there anything that can be done with the current POW/POS mechanism for blockchains to lower the environmental impact that they're having around the world? Or does the community turn a blind eye to this.

Is it really reasonable to accept the amount of bad actors in the community and to say that this is a protected, safe way for people to transact - or even really invest? What impact do instances like the Terra collapse have on the communities mindset towards regulation?

I'm genuinely curious, because i've never seen these questions really answered in a way that convinces me that cryptocurrency is anything other than a high volatility, speculative investment market.