I would say the free games are a bread and circuses approach. I now have a massive library on Epic, and I only paid for one of them (Old World). I will continue to get their free games, and have quite happily enjoyed several of them (Subnautica was absolutely fantastic).
I, like other users here I will wager, view Steam with vague annoyance as it has not caused any major personal issues. I bought HL2 on release in 2004 and had to wait a few days to download the updates over our dial-up connection. It was quite the letdown to have to wait. I've never been without a halfway decent internet connection since then, so the worst aspect of Steam had been nothing more than a minor or temporary annoyance for me. I can fully believe that this aspect makes Steam a complete no-go for some users, though, and it is inherently anti-consumer to make it so unnecessarily difficult to play your games offline.
On the flip side, Steam has done a lot to make my gaming life dramatically easier. A lot of Steam's features are designed to remove barriers to playing your games (with the glaring exception I mentioned earlier). I remember spending hours fiddling with firewalls and IP addresses and other opaque settings to get Age of Empires II working at LAN parties in the early 2000s. Now, if I want to play with my brothers, there are no barriers, and as someone who grew up with those barriers, this is an enormous positive, and one for which I admit I will overlook quite a lot. Automatic updates only help this, as we used to have to hunt down patches or no-cd cracks or whatnot to make sure everyone was on the same version of the game.
Downloading mods is easier than ever, and it is great to have automatic updating of those as well. But, it is quite anti-consumer that you cannot by default download Steam workshop files without having the game and being logged in.
I find that I also appreciate the silly little touches like achievements and cards and badges, which serve no other purpose than to get you more firmly entrenched in the Steam ecosystem. It's fun (even though it's pointless) to hunt for achievements which can encourage you to try things you would never have attempted before, although a vast number of achievements are mind-bogglingly poorly thought out. Judging by the achievements, many developers have a much higher opinion of their game than it warrants.
Other features are quite nice as well, like cloud saves, Steam Link, big picture mode, Proton...it's undeniable that Valve has invested a huge amount into making Steam a one-stop shop for gamers, by eliminating barriers once you are in the ecosystem, and if you are highly invested in Steam the features really are fantastic. But the goal is to keep people within Steam, of course, and any other read of Valve's investment in those features is purely naive.
Steam refunds are an obvious example of Valve's motivations. It took YEARS for them to start offering refunds, a basic service for ANY store, and that was only because of legal and political pressure from more consumer-friendly countries (i.e. NOT the US). There would still be no refunds without that.
I am fully aware of Valve's motivations and Steam's shortcomings, but the benefits - so far - have drastically outweighed the objectively anti-consumer crap that Valve regularly pulls. I have built up an enormous library of games at a fraction of the investment it would have taken through retailers, although in the last few years other digital distributors have caught up in that regard (seriously, the early years of Steam sales were really something else). I have played games with friends with an ease that I just never had before, and I've discovered a host of games and developers that I would never have tried (and arguably, they would never have been made) without the ease of publishing that Steam allows.
I would honestly love to buy all of my games on GOG, but the games I am most interested in are mostly just not there, and to be 100% honest the storefront is secondary to the game for me. That's not the fault of GOG, and is indicative of how publishers have now invested wholesale into Steam. The last game I bought on GOG was Into the Breach, a fantastic single player game which just didn't receive any real benefit from Steam's ecosystem (I've now bought it a second time on the Switch...).
Valve has benefited from me, yes, but I have also benefited from them. I have invested in Steam's ecosystem with eyes open, and found it to be useful enough to stay.