I have 11 alts and many of my guildmates range from 0 alts to 5 alts, I have spent $200 and most have spent none and we are within 10 item levels of one another. It’s a small scale example but its more so the meaning behind it.
Alts are optional but are overall more beneficial than not having them. Paying into what you refer to as a predatory system will get you some progression but it will only get you so far. There is a really good YouTube analogy from a KR player in Korea that talks about it.
Tl;dr it’s like having a super car and a slow car at a red light, the super car will hit the next red light faster but both cars will end up waiting at the same red light which is why I say paying for anything is not necessary.
However to your other points, just like any game since lost ark is more PvE focused naturally the best things will come from high end PvE content, and unfortunately in respect to your post there will only be more mechanics where 1 person can kill everyone and you require a synergized run.
Also unlike Argos in legion raids you do not get the option to revive mid-fight if someone dies like you do in Argos so there is more difficulty ahead.
I think the road map is being done in a way that promotes f2p players to be ready for content while doing some things along the way for those that are already at “endgame” and we will see how it all plays out but it does look good from a glance right now.