Does Adobe reject photos for technical issues no matter the equipment?

Show us one or two examples of assets that were refused and the reasons for refusal.

We can provide better feedback that way.

• As Stock inventory increases closer to 1 billion assets, there’s greater competition from other content. Getting accepted is harder now than it was in the beginning. 
• Before submitting, compare your work with similar inventory to ensure yours is better and more unique than what Stock is selling.
• Find a need & fill it with relevant content.

https://helpx.adobe.com/stock/contributor/help/reasons-for-content-rejection.html

https://helpx.adobe.com/stock/contributor/help/quality-and-technical-issues.html

https://helpx.adobe.com/stock/contributor/help/how-to-submit-distinct-content.html

https://helpx.adobe.com/stock/help/find-similar-assets.html

You have better control with a DSLR/Mirrorless camera than with a smartphone, regardless of the make. In my view, although such cameras can produce good results, it falls apart in challenging conditions. A lot of the hype is marketing!

The quality requirements are the same regardless of the equipment used. Yes, you’re more likely to achieve the desired quality with a full frame camera than a cellphone camera; however, under the right conditions, cellphone images can also be acceptable.

No matter the equipment, but sometimes it can be difficult to see what's wrong with a picture with 'Technical quality problems'. But it would be helpful if you uploaded one of the pictures.