Hello, person with farming experience and degree in horticulture here
sorry but this got pretty long ^^;
@DokiDokiTsuna I've never thought the issue with GMO's has been considered the DNA you're consuming directly, but rather the substances in the crop that are being produced by the DNA, etc.
Two potential ways that GMO crops could conceivably cause harm are:
some crops are modified to be resistant to herbicides, which allows for greater herbicide use. If the herbicides are considered to be harmful and this leads to greater residue on crops, this could be an issue. But I will mention that regulations exist as to how herbicides are applied, at what concentrations, how many days must pass between application and harvest, etc.
some crops are modified to produce pesticides directly in their tissue so that they don't have to be applied in the field. If these pesticides are considered harmful to humans, this could be an issue. Many pesticides are indeed very harmful to humans, to the extent that regulations require those who apply them to wear protective clothing (ranging anywhere from long sleeves and pants to full-body suits with gas masks). However, I really, really doubt that any of those seriously harmful ones are actually modified into plants. By far the most common modification of this type (that I'm aware of) is the addition of DNA that creates Bt-toxin, a substance that is poisonous to many insects but is considered safe enough to be technically "organic" and is commonly used on organic farms.
Overall, I think it's a mistake to make a blanket statement "all GMOs are safe/unsafe" - that's like saying "all medicine is safe/unsafe". All types of GMOs can be totally different depending on what DNA is actually involved. A bit of DNA could produce a leaf, human hair, or snake venom, depending on what it is - and each GMO's safety can only be evaluated on a case-by-case basis.
Regulations exist of course, and companies can't just release any GMO crop they want all willy-nilly without conducting safety trials. But some people don't trust the government or corporations to be fair or thorough enough, and/or don't trust that the studies aren't conducted without "special interests" involved.
It's worth noting that it's fairly easy to determine whether something has acute/short-term effects (just feed it to some rats and see what happens over a few weeks), but much harder to determine what chronic/long-term effect it may have. It's entirely possible that some GMOs do indeed cause subtle harm to the human system over many years, but nobody has established it because it's impractical to run studies that long. Some people say this is the most likely source of the relatively recent rise in allergies, disorders like autism, etc. (either that or vaccines, but that's a whole different debate).
Also, random fact - "organic" foods aren't necessarily non-GMO. It's possible this could have changed since then, but a few years ago I was looking through the paperwork needed to get an "organic" certification (in the U.S., not sure how it all works elsewhere) - and organic farmers are required to use non-GMO seeds unless they aren't available for some reason. I don't remember the exact wording, but it was basically that you have to try to use non-GMO crops, but you don't really have to if you have an excuse.
Ultimately, am I concerned about GMOs? TBH not really, although I'm not entirely dismissive of those who are. Special interests influencing the results of studies (and lobbying to influence the regulations in the first place) is a reasonable concern IMO, even if I'm not sure to what extent it actually happens. And even the "experts" likely don't know a whole lot about what subtle long-term effects some of the products may have. It's easy to just draw a conclusion - "GMOs are bad" or "it's all just hype and fear-mongering", but the reality is that none of us actually know anything for sure.
Personally, I just try to eat healthy in general - no use worrying about GMOs if you already live on sodas and junk food XD. And if at some point I end up dying an early death due to some kind of harmful GMO then I'm cool with it. Gotta die at some point anyway, a little sooner won't hurt ^^