Yes, we know, but the alternative isn’t “just don’t buy one because it doesn’t matter anyway”, it’s “Do the best we can as consumers to make smart, green choices”. Vote with our wallets that we do want greener alternatives rather than giving up. If a battery comes along that is more eco friendly than lithium I’ll probably buy that one.
A better way to phrase what you said to encourage people to go green is to say “Absolutely going electric is a smart choice, it’ll reduce your personal emissions by a substantial amount, but remember that to public transit/walking are still the greenest options. We can also always demand from the companies we buy from that they should use greener manufacturing as well.”
Don’t just point out the flaws in a way that comes off as “We shouldn’t even try because what’s the point”. We can both be better ourselves and demand companies hold themselves to even higher standards, it’s not one or the other.