But there are also tipping points. It's easier to rationalize some gamist structures from an in-character perspective than others. This isn't a board game. This is a role playing game and the in-character perspective is an important element that doesn't exist for board games.
Again, rationalize the cleric. He only gets a little bit of help from his deity at level 1 because... what?
Is it because he's not pious enough? Maybe at level 1 all clerics are like 'meh, I heard about this god guy, he seems kinda neat' and by level 15 or so they're like 'oh, lemme tell you about Pelor! He's this great guy who is totally the best god..."
Or maybe God doesn't want you to really help people until you gain a few levels. Like 'oh man, that bugbear could easily be taken out with one sixth level spell, but God wants us to leave it alone and let it eat those villagers, because at level 1 there's no real way we could handle it.'
Or possibly people just don't count to any deity until they've killed a dragon or two. Maybe the lawful good deities are just like the evil deities - they don't really care about the average peasant, they just care about the people who can do cool things for them, and the cooler the things are the more they reward them. God as a crowd in the Roman Coliseum.
Or maybe it's a gamist structure that doesn't allow clerics to wtfpwn everything at level 1 even if they're very pious, because clerics wtfpwning everything at level 1 is bad for the game.
As Gygax said, the very concept of 'realism' in a medieval fantasy world with Dragons, Wizards, singing Bards who can change reality with their songs, Gods, Demons, and every other D&D element is... absurdist. Totally and utterly absurdist. If you think that a particular element doesn't make total, perfect, 100% sense in a world where a dragon can swoop down and turn into a beautiful prince to seduce the princess then leave her with half-dragon babies that she can bear without any real issue (lets go into the genetics of that for a second, shall we)...