Is it bad to post a song everyday?

It's a lot of work. It was my intent to do that on the folk oriented blog I started in 2005. I kept it up on a daily basis for 4 or 5 months and then slowly slacked off. Posting daily seems to work. When I stopped posting regularly I saw traffic drop from hundreds of daily unique visits to scores of daily visits -- and on down.

No one has any clue and if they tell you they do, they are lying or wrong.
Literally millions of people let their songs simmer and get zero engagement. Some people only release a few songs per year and get hundreds of millions of streams. Some people release music nonstop and it works for them. Some release nonstop to nobody.
Release timing mattered a lot with traditional promotion, but in the age of social media algorithms deciding your fate, there is no magic formula. Your personality and how you show it and the songs make a difference, but there’s also no formula that can guarantee that stuff (just look to the failed industry plants that had every advantage).
The best thing you can do is be true to yourself and do what you enjoy. Then any fans you get are fans of your actual authentic self.

Hold something back. You don’t want people to get jaded, and you want to give people a chance to become familiar with your music. Also, keep a stash for those times when you know you should post, but just ain’t feeling it lately. Dumping too much in a short time just waters your work down, and people won’t remember it. Just your best stuff-wait until people are asking for more, then hit them with something really good.