Feeding birds in winter isn’t necessarily a good thing and at least one study has shown that birds lay lower numbers of eggs when fed well, perhaps due to an unnatural unbalanced oil-rich diet: https://blog.nature.org/science/2015/01/05/winter-bird-feeding-good-or-bad-for-birds
However, there are many studies showing the opposite. But is good winter survival and artificially high populations necessarily a good thing apart from entertaining us and increasing awareness of the natural world.
Then there’s the spread of disease at bird feeders as with the greenfinch (grønnfink) in the UK (populations plummeted and bird feeders no doubt contributed to the spread).  That birds are discouraged from migrating and stay in the same area year round can also lead to greater exposure to disease.
But what about the production of bird food? That happens often in large fields, mostly using conventional BigAg non-organic systems which directly impacts local bird populations by pesticides and habitat loss. Here in Norway, little of the bird feed is grown in-country. 
For these reasons, I try as far as possible to provide natural food for the birds so that they can find alternatives and I can delay putting out food as long as possible. Home grown apples are put out for the thrushes, I tidy seed heads in spring and nettle seeds loved by finches are allowed to hang all winter. Local grain can also be put out for yellowhammers (gulspurv).
In the case of goldfinches (stillits), their main food is burdock (borre) and I have introduced Arctium lappa (greater burdock / storborre) to my garden for them and greenfinches (grønnfink). However, at this time of year they tend to move over to the birdfeeder.
Here’s a couple of videos from the weekend of these beautiful birds that once were rare in this part of Norway, but are becoming more common each year. See other goldfinch posts here: https://www.edimentals.com/blog/?s=goldfinch