The problem isn't the inability to purchase pink wards against stealth late-game

The problem is that Riot to remove stealth's counter in a half-assed way.

Having stealth with counterplay is reasonable. Having stealth with no counterplay is also reasonable, since that allows you to balance stealth around the idea that the opponent can't counter it by getting a 75g item.

What Riot has done so far this season is move towards stealth with no counter by removing the true sight from sweeper without removing it from pink wards. This is the worst of both worlds. It's frustrating for most players because countering stealth is clumsy, but it's also frustrating for stealth champions because now their kits have to be balanced around the idea that stealth is mostly uncounterable.

What Riot needs to do is either revert back to the way things were before or finish the job. Stealth would be in a perfectly fine position is true sight was removed from the game entirely, but champions with stealth were nerfed in return. Now stealth champions don't have to worry about being made useless by a 75g consumable and everyone else doesn't have to worry about having a pink ward on them at all times.

Tl;dr: Remove true sight from the game, nerf stealth to compensate , no more worrying about pink wards.