You actually can, there is some ways you can do it:
1. Sellers of "normal" stuff will take USD if you "deal" with them, for example if you need to buy a motherboard, most likely the seller will instantly say yes to an USD offer before getting paid in VEF because the money wont get devaluated in USD, if you check mercadolibre.com.ve (ebay equivalent in venezuela) you can see alot of people offering USD.
2. USD is used for properties such as cars, houses, land, etc. If you want to purchase/sell some of theses you pretty much have to pay/get paid in USD, not in VEF. Of course this is because devaluation is so big that if you sell something in VEF next day you can just lose 5% out of nowhere.
3. If you own a USD debit or credit card, you can use it within Venezuela payment networks, you just wont get the black market rate, you will get the dicom rate that is currently 119.850,00 VEF per 1 usd.. while the black market rate is around 3.200.000 VEF per 1 usd, so you definetely can, just that you wont get a good rate.
And last, it takes some 10 minutes or less to deal exchange of VEF to USD at black market rates, you just need to have the most minimal social interaction, as everyone has friends, family, acquaintances, coworkers, etc who is changing this, it's just such a natural thing to do, dont let the name of "black market" make you think that is some shaddy thing that you need to do where you risk your life, its just some natural exchange of currency that most venezuelans know how to deal with.