Shade for my Cactus and Succulents.

On some really hot days i have had quite a few cactus and succulents burn and lost some, mainly succulents.
I have always worried about the sun and heat burning more Cactus and Succulents.

I have put some 64-70 UV block out shade cloth on my greenhouse to stop the strong sun after cutting back hard a tree next to greenhouse.

I wanted to protect my Variegated plants, Euphorbias which have gone a very light pale mainly the crests, and the light pale on hylocereus grafts.

Is there such thing as too much shade for such plants and others in the collection???
Would it cause issues for my other plants? or should i just keep growing the same way i have been growing for years??

Any advice very welcome!!!

It really depends on the types of plants you are growing. A lot of euphorbias with deciduous leaves will make larger leaves in the shade and plants might look less "hard" grown that way.

Later in the season you may find burning to not be as much of a problem as the ozone "hole" clears up and we get less UV light.

I grow most of my plants under medium shade and they seem to like it. Even then some variegates will burn and I find Mammillaria Fred does too. I give extra shade to seedlings(note some species like Ariocarpus are still not fully mature even when they are nearly a decade old) and haworthia as well to avoid stressing them too much. I think with variegates some are so lacking in chlorophyll that they will burn regardless of light levels and this is probably caused by the tissues that are without chlorophyll being unable to sustain themselves over the long term. Sometimes they will be fine for a few years then burn coming out of winter into spring, I would say this is more likely related to their inability to produce energy required for metabolic processes via photosynthesis than it is due to light levels.
I think in habitat lots of our plants find niches that are shaded to a certain extent, nurse plants, rock crevices and even being covered by dust and debris acting as a sun shield. Others pull themselves into or underground during the hot bright seasons. On top of that here we have the ozone hole as Cereoid points out and we also get stronger sunlight in the Southern Hemisphere due to the Earth's orbit being a few million kilometres closer to the sun during our Summer than it is during the northern summer. It would be a lot hotter here too if it were not for the fact that there is a lot more ocean in the south.
The only issues with too much shade would be etiolation(plants stretching) and perhaps plants would be slightly more susceptible to disease. I have a light meter and it tells me that even under old dirty medium shade cloth light levels still top 5000 footcandles by early spring. This amount of light is considered sufficient for cacti grown under artificial light conditions. Most important is to gradually introduce plants to stronger light levels and I also find that a bit more shade in the few weeks after repotting doesn't hurt.

Thanks all for your advice, i will keep an eye on it for the moment, we just had some very hot days in Sydney.
I think the extra shade has helped heap over the last few days, i usually throw some paper towel over my vulnerable plants.
I most likely will keep the extra shade on my Haworthia's and Agave, will see how things pan out, thanks.