To be fair, it's pretty rare for a developer to have a game flop this hard and then spend so much time and money to update it for free. They've had several large content patches over the last two years and haven't charged a penny or abandoned the game. A lot of devs would have taken the launch money and run.
I'm a bit more tempted now to get this, but I'm not sure how much time I can really commit to it with everything else going on. Reviews have been very positive (~5:1 in favor) since the new update: https://store.steampowered.com/app/275850/No_Mans_Sky/
There's a fairly lengthy interview in The Guardian with the lead developer that goes into what went wrong and how they're fixing it.