According to the article itself, such transactions have been declining by as much as 50% in the last few years - which means that BTC is less and less used on the dark side.
Bitcoin itself has been seeing really, really low percentages since at least 2016/17 for illicit purposes, actually, according to research by Elliptic themselves. Perhaps that percentage was/is higher on LBC, as a trader there I do get quite a lot of dubious offers if I leave a sell offer. That actually hasn't really dropped since enhanced KYC (if you sell micro amounts as $100 and below doesn't need KYC).
I've not used LocalBitcoins in years since they started asking for KYC, but who is still using them? What niche are they filling?
There are still quite a few countries where there are no functioning exchanges and with very few options to move money to those abroad. They have gradually shat all over what made them worthwhile for most users, but even if they lose a lot of custom now future custom in that niche may make up for it.
I'm still a user, a freelancer earning and invoicing in Bitcoin, and remote working. Living and paying bills/taxes over two or three countries at a time. I dont'know any exchange that will send me my money instantly if I sell my BTC for two of the currencies I use. For countries in Southeast Asia like Malaysia, Indonesia, Singapore, Thailand, Vietnam, if you use LBC to sell, you can close the deal, with escrow protection and instant bank transfer (yes, actual real time money in your account, not SEPA "instant" or "same day" haha) in under 1 minute. Over the years, I've also built up a network of peers I trust, I SMS them, they open a trade, I take it, or the other way around.
Rates can often be much better too than exchanges.
If you don't mind KYC and don't mind navigating scammers in the beginning, LBC's pretty all right. Localcryptos and Bisq though are where I'm looking to go, except volume is not so good, and that network of trusted users isn't there.
Hope I explained why p2p platforms are still popular. As gentlemand says, they shat on us users a lot over the years, so we're slowly migrating but for sheer convenience and options for travellers, you can't find better than this.