I just want to walk back a little on that title because it's a pretty strong statement. I don't mean all newbie corps suck all of the time. There's more nuance than that.
It's kind of easy to forget, but games didn't always have central forums. Sure you'd have a developer's "official" forum, but for the most part discussion would go on either ingame, or on different fragmented community forums. However over the last few years Reddit has become something of a defacto "townhall" for a lot of games with EVE being one of the more notable examples. Now personally, I quite like this. I'm a big fan of Reddit's format and /r/eve is by far one of the better communities I've had the luck to come across. However that centralisation has some downsides especially for newbies joining up today.
So let's say I heard somewhere that EVE went free-to-play and decide to go check it out. I sign up, make my alpha clone account, and spend a couple hours on the NPE. Man this game is cool! The next day I'm on my phone during lunch. Reddit is the 8th most visited website in the US and 26th globally, so there's a decent chance I come across /r/eve. Even if I just google "EVE Forum" in incognito mode, it's the 15th result. Upon discovering /r/eve, I immediately come across this top post. Great! It's got lots of upvotes so it must be solid advice. There's a lot of info in that post, so you think to yourself "man this game sounds hard, I should join one of those super newbie friendly corps and get help!".
So you then join a newbie corp and start looking for this help. This is where things get a bit controversial.
With the exception of the fantastic public EVE Uni Wiki, this help does not take the form of "here's a huge pile of useful information about EVE Online: A Spaceship Game". For the most part, it's "here is the most basic information required to be a faceless line member in our enormous MMO guild". There's nothing about fitting, ships, piloting, various ISK making methods, alts, wormholes, mechanics, markets, production, etc. Just, "here's how to set up jabber/mumble and anchor on the FC". Now day 1 sure, there's nothing wrong with that. EVE is hard and those are the questions people are going to ask during the first week so it makes sense.
But where do you go from there? Where's the "teaching"? I mean you can ask questions, but truth is in most newbie corps (BRAVE being the prime example of this), there's far too much "those who can't do, teach" going on. You have people who've never FC'd anything bigger than a 30 man T1 cruiser fleet giving FC classes. You have people who've got about 3 solo kills in their entire EVE career sperging about their amazing solo Apoc fit, and you have folks who've never done better than a 30m tick talking about ratting like they're Gordon fucking Gecko. It just gives a really false impression of the game and a lot of bad/wrong information.
Then you get to the sandbox aspect of it, what goals do you have to achieve? Sure it might be cool to finish training for that doctrine ship, but that's purely a function of time spent subbed. It isn't a reflection of your efforts and the victories of your larger corp, alliance, or even worse; coalition feel pretty hollow when you're just one of a thousand nameless cogs in a huge war machine.
EVE as a whole right now is suffering from a severe lack of "content creators". That isn't a euphemism for "FC", it just means anyone who's willing to pick up a spade and start shoveling sand from one side of the box to the other for any god damn reason they feel like. The guidance within most newbie corps is exactly not that. It's don't rock the boat, don't train for random ships, don't shoot these guys, do this thing, do that thing, and so on. Instead of a sandbox experience, you're just playing a regular old theme park MMO except the quests and rewards are defined by other players as opposed to the Developers. My argument would be that the feeling of gridlock everyone feels is more about a lack of independent actors than player counts.
It's possible to argue that in itself is part of the sandbox, but in my own experience from the perspective of a new player it doesn't feel that way. It's far too easy to get the impression that there's some barrier to creating your own content whether it be ISK or SP, and everything about the current crop of newbie corps only serves to reinforce that view. For all my other disagreements with the guy, Wingspan is a perfect example of how untrue that is.
Despite all of this, there are a lot of folks who've seen or read of the big battles/wars and want in on it. Cool. They serve a purpose in that respect. My own experience as a new player was flying shitfit tackle frigates in Dreddit during the Fountain War and I thoroughly enjoyed it. But again we go back to that Alpha clone advice thread. The advice there as it is in any newbie thread is "join a newbie corp right now". They have their benefits, but I'm not convinced that funnelling the entire incoming player base into the same half-dozen corps that all provide a virtually identical playstyle is necessarily a good thing for the long term health of the game.