Genetic engineering means to directly manipulate the genes of a given organism, whether it’s bacteria or plants or vertebrates. The general technique is now about forty years old. Nowadays there are myriad ways to do this, the latest one being CRISPR-Cas9 or similar systems of gene editing.
Human beings have been playing with the genetics of domestic organisms we breed ever since the dawn of agriculture. But this was done by selective breeding, which is less precise and slower.

What has changed is that we can excise a gene from a species and introduce it into the genome of another species, or delete a given gene (we call this manipulation a “knockout”), or modify or mutate a given gene or DNA sequence pretty much at will. The process is more precise and much, much faster.

The reason I think it has been largely advantageous is that there aren’t many examples of genetic manipulations with bad consequences, and there are countless examples of good, beneficial developments.

Using genetic engineering techniques, we have accumulated a large body of knowledge on how cells and organisms function, and understanding these basic processes in biology is a way to understand the causes of human disease, and the opportunities to find new ways to cure diseases or otherwise improve human health. For example, by creating mouse models of cancer.

Genetic engineering has also created the famous (or infamous to some) GMO plants of agricultural importance. Although there could be negative aspects of the spread of GMOs (reduced biodiversity, negative environmental impacts), there are also advantages to feeding people when it wasn’t possible before.
Of course, no technology is ever completely “safe”. I’d argue no human activity is ever completely safe. But the reality is that there isn’t a single example of a catastrophic consequence of genetic engineering. Hopefully we can keep it that way.

I sometimes compare genetic engineering to cars. I’m sure when cars were invented people wrote dire warnings about how the high speed would result in crashes and the loss of human lives. And surely, cars kill people and are dangerous. But nobody thinks about banning cars. People try to build safer cars and safer roads instead of banning the technology. It's the same with genetic engineering.