Two ways to look at it, I guess.
That said, there are a handful of appliances I have torn down (among hundreds) where I wondered how the appliance had gotten its regulatory approvals.
For example, I recently repurposed a new, name-brand toaster oven with a reflow oven controller and was surprised to see that approved appliances may feature long, uninsulated metal assemblies connecting the heating elements, covered only by the exterior skin of the appliance and featuring a small air gap. One dent into the side of the oven and you'd have a direct short to ground.
Friends of ours had their DCS range weld itself shut thanks to a interior short.
When I took apart a failed (un-modified, just used) toaster a couple of years ago, several PCB holes no longer featured solder due to overheating.
Thanks to crummy design, a Kenmore vaccum cleaner in my home almost caught fire last year. Fully-approved unit but you can't help stupid when it comes to designing an power interface where large inductive currents pass through 2 comparatively small connectors that are repeatedly connected and disconnected (as one does with the wand/floor thingie on a vaccuum).
Most CO detectors sold in the US are built to a specification (UL-2034) that expressly allows long-term CO-poisoning. As a result, I gift friends with furnaces who are expecting with a CO experts unit. Most think its odd until I explain the issue.
ABYC allows the use of untinned wiring on ocean-going vessels, as long as you use some sort of connector on the end that may or may not keep the water from the wire.
In MA, a piece of plumbing hardware like a bathtub is not considered 'safe' to install, unless the manufacturer has paid a local license fee. Not sure if the license actually involves an outright review of the product or if it's just revenue collection. Either way, if a un-licensed piece of equipment is installed, the plumber doing the work is liable for any damages.
Bottom line: Approvals can be useful to help prevent the most obvious issues. However, they are not by themselves a guarantor of quality or adequacy. After all, many safety standards were written by industry and adopted by the 'regulatory' agencies that derive their income from said industries. Foxes guarding the henhouse and all that.
But, such standards are very useful when comes to defending lawsuits - the device 'met all applicable' regulations, right?