I have the Panasonic Lumix Fz70 and it is denied for alamy for the same reason. I bought this because of the great zoom. But the 1/2.3'' sensor at least for alamy isn't enough as they require larger. Apprently it doesn't matter if your shot looks good at 25% or 80%. It's mean to still look clean and crisp at 100%. Notice that many camera's from 100-500 dollars rarely have pictures that you can zoom into 100% and still look good in quality. I believe that 1/2.3'' is something like 14mm or so. I believe that you should get at least a 22mm sensor camera, and if you can get something like the nikon d610 which has a 36mm sensor (that's like basically 1.5'') then you won't be rejected by any website. Of course you will be paying a lot of money, 2k for the camera and then a bit extra for the lens. You probably won't even make your money back unless you are a really good photographer and travel and find great things to photograph. So don't invest too much and think you are going to make much money. You are better off posting your photography for free on a website and just having ads on the top and side of the website to earn you money. (especially if you are wanting to use a 1/2.3'' camera). Alamy has these restrictions because they want to make sure that it was taken with a high end camera, not a low end or medium range camera. Regardless of how good the shot is, because a business may want to display the image at 100% blown up on a big poster or something. And with a 1/2.3'' camera that doesn't work very well, it only looks good printed probably on an A3 sheet and no larger. They want to probably give the buyers large enough MP photo's with good sensors so they are clean at 100% so you could print them even at A2 and A1 sizes and still have it look crisp and nice. And to do that you also need enough MP also, you want high MP and a large sensor. 24MP with a 36mm sensor is very high quality. It should be able to print even at A1 size and look very nice.
Apparently the sensor on that is 1/2.3''. The sensor is the same size on my Panasonic Lumix FZ70. It takes really good shots, but I would say mine get the same message as yours because of the image sensor being the same size as yours. I would say to take photo's that they consider acceptable you would have to spend maybe at least $800 (not just $400 like I spent). Of course you probably could post your photo's to other websites. The Canon EOS 1300D isn't much more, about 600 dollars. It's sensor is a bit large, it is 22mm I believe. Compare that to the 1/2.3'' which would be 14.14mm. So you can see the Canon EOS 1300D one compared to your camera and my camera has a sensor 8mm larger which is significant. At the same time I wouldn't risk paying that and having possibly Alamy reject it also, I would go a bit larger like something like the Nikon D610 which has a sensor of 36mm. It's a $2000 camera without the lens, there is no way Alamy would reject it. Of course after you buy a lens you may have spend around $2800 all up and unless you are a very talented photographer that travels around and takes lots of photo's then you will probably never earn your money back off your photo's. If you have a $500 camera and you are taking good photography, you should just put it up for free on the internet on a blog or something and put ads on the blog and you can earn money that way. Either that or find another stock image site that isn't as strict (I am not dissing alamy BTW, the fact that they are strict probably is a good thing for buyers).