There is certainly a place for games where all functional content is always available to all players. Any game that is a serious e-sport with lan events and big real money prize pools should definitely be like that. For games that aren't serious e-sports, I think some level of exclusivity of things that provide a competitive advantage can be tolerable as a way to motivate players to strive to have that advantage, but it should be limited in magnitude, and it shouldn't be impossible for new players to get started. For example, the boosted sets in TC2 provide a competitive advantage, but it's not such a huge advantage that new players can't get platinum and obtain future boosted sets.
I have played Wreckfest, I've got all the tournament cars except the Hotbomb, and have 430k of the 500k fame needed to get that final car. I will get it at some stage, but despite having owned Wreckfest for 10x as long as I've owned TC2, I've played TC2 for 3x as many hours. I played Wreckfest more when the tournaments needed you to finish fairly highly relative to other players, it's far too easy now. I generally comfortably get the gold tournament rewards first attempt, so it only needs me to run the game for a few minutes every few weeks to rack up the fame. There just isn't anything in the game to provide an incentive to do any more than that, and I'm not sure it's even worth getting the Hotbomb as what will I do with it when I have it?
Cosmetic content is a different matter, and I think it's fine to have extremely exclusive cosmetics. For example, the highest level of seasonal cosmetic rewards in Rocket League are only obtained by the top 0.01% of players:
This season's competitive rewards have been revealed to be Wheels! Only a couple weeks left to rank up!
www.rocketleague.com
This is probably a better way, overall, to motivate players to play, but not every game is able to make cosmetics so appealing. Even though people clearly want the higher level cosmetics in Rocket League, I'm not sure how much value they have in rational terms, as they are devalued by so many people buying them for real money, either buying a farmed account, paying someone to log into their account, or paying someone / getting a friend to carry them to a higher rank in a team mode to get higher season rewards for them.
I think all this is something the industry will continue to work on, but for now, TC2 has put itself firmly in the camp of "grind to win", where you invest time to have a competitive advantage over other players. The biggest part of that competitive advantage is always available to everyone (grinding parts sets, grinding bucks for cars). They've sensibly kept the exclusive elements of competitive advantage fairly small. I think it's valid to have some games out there that are like this, and players can choose between playing such games, or a game like Rocket League where there is zero exclusive competitive advantage available. There's also a place for games like FH, with exclusive competitive advantage available, but very easy to obtain, so basically anyone who logs in and plays during a specific period will get it. I think it would be a mistake for Ivory Tower to assume that FH4/5 have more players than TC2 because of this difference, though, I feel brand strength is the bigger factor.