I don't know that this is true. I certainly wouldn't be surprised if there aren't some mint state Lincolns that didn't have many graded ten or twenty years ago and there are now large numbers but I believe this can be ascribed to market demand rather than loosening of standards. Every indication I've seen has suggested no loosening, though admittedly, I'm not extremely familiar with this aspect of the markets.
There's always been some hype in the market and it did seem to pick up in 1986. This was probably because coin sellers now had what they considered an objective measure for their coins. Now instead of just claiming it was one of the finest known they could tell you how close it was to the top. But other than the US mint all the hype has always been only for the classic coins. NGC wouldn't wouldn't even grade moderns at first and PCGS wouldn't allow them in the registry. You can't get farther away from hype than that.
Twenty years ago there wasn't a single clad quarter on the PCGS pop reports. Ten years ago mint state clads had only just started getting submitted. Now days there are nearly as many graded moderns as graded classics.
For everyone who thinks that grading standards are different by 2+ grades, can you please provide us with some examples where an older holdered coin is of the same quality as a newer holdered coin but the grade is lower by at least two grades lower? Saying it is easy. I think you will find that proving it is not. Here, I will make it easy. Find me a Bicentennial Silver IKE that looks like this and is graded MS66. Let's see em guys!
Nice 68 - I've been buying some 67 Ikes lately. The 68's are definitely nicer, but don't agree with the huge price difference.