I’ve bought every Stellaris DLC over the years, and I’m not even a particularly avid Stellaris player (347 hours played (which while notable is peanuts compared to the superfans’ hours) and haven’t played recently). Here’s my thoughts on it:

I buy DLCs day 1 that I am supremely interested in, and everything else I pick up on discount either during a sale or from another site (not sketchy key resellers - I use isthereanydeal.com, which lists more legitimate sites). In multiplayer, all players can use the DLC the host has, so I’ve been the dedicated host for my friend group there. I don’t think the massive amount of DLCs is good, but it is at least tolerable (I liken it to a subscription model) and I enjoy how the devs share some of their insights during the development process. Despite all the flaws it has, Stellaris is a really cool sci-fi 4x game that probably has the least ridiculous learning curve compared to other Paradox strategy games.