Do your research.
Whilst it's true that there are a lot of empty premises in some areas, there are still plenty of locations where prime retail premises are hard to find and so remain highly priced and with little non-occupancy. For example, in my village and the surrounding villages, there isn't a single empty premise suitable for retail or offices - when a shop or office closes or moves, it's rented out again virtually immediately.
Even in run down areas with lots of empty retail properties, there's still the scope to make a decent return if you choose the right one to buy. The prices to buy will be a lot cheaper, so if you get one that is in fairly good condition, with flexible space and decent services provision, you should stand out and it should be rented more easily than nearby shops that aren't as good.
In the "run down" end of our nearest town, there are lots of empty shops on the once prosperous shopping streets (not recent, the area has been in the doldrums for 20 years or more!), yet whilst some shops have not had any tenants at all for years, others seem always occupied even though the tenants come and go. These are the ones with modern services (power, water, heating), multi use interiors (i.e. back rooms for storage, offices, changing rooms, or whatever), and a decent location (corners, close to main roads, better on street parking outside, etc). Even in the run down areas, there is a need for retail, such as off licences, convenience stores, tattoos, tanning studios, hairdressers, dress agencies, etc.
You could argue that a couple of "cheap" properties costing £40k and bringing in rent of £4k p.a. is just as good, if not better than a more expensive property costing £80k that brings in £8k p.a. There'll be more people, especially in a down turn, able to pay £4k p.a. to take a punt on starting a business than there are able to pay £8k p.a. in a better area.
You just have to do as much research as possible. The days are gone where you could buy a property, any property, and sit back and watch it rise in value and give a good income return. You have to get it right these days. It's not for uninformed amateurs. You need to know your market inside out.