"Industrial supplier" meaning what? Commodity hardware and components, custom machining, weldments, castings, forgings, extrusions, mouldings, etc etc. Any particular thing that you're looking for? I've had very good success using a number of these sites for very specific items, sourcing perhaps 50 or 60 custom components and assemblies from a dozen sources within the last several years. The due diligence is on your part, and not so much the website. These B2B websites often do not have much in the way of pre-qualifying vendors, so as in any transaction, caveat emptor. There are a lot of middlemen out there acting as trading companies or business agents, particularly with the Asian sourcing sites, whereas your best chance of success is directly with the factory or producer, in my opinion.
It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.