Besides the darknet and various markets, there are also many services which do legitimately accept Monero. So nothing will happen to Monero just because a mutli-coin wallet decides to cut support for Monero addresses. Genuinely speaking, it's better to use a dedicated wallet for Monero anyway, so that you can manage the seed phrase properly. (It is of a different format to Bitcoin.)
The concern for monero losing its user adoption should be taken seriously though. If it is going to be darknet only coin, no point in holding it as it will be completely isolated from the real world. I still hold because I don’t want to believe that.
I am leaning towards NotATether's opinion in this discussion. I am still using Monero to pay for legit services that are offered on the clearnet and that are absolutely legal. As long as I can do it, I will keep doing it.
And another aspect to keep in mind, is that Monero is also used for P2P trading a lot. I recently sold two old/vintage PlayStation 1 games for XMR.