SuperRigger.808: I haven't seen many older games being brought to the storefront in a while. Mostly the same new early access titles that steam gets.
What's going on that we're not getting any more classics? Quarantine, anyone?
The number of old games GOG releases per year fluctuates, of course, but unless you're
super restrictive in your definition of "old" (like Canuck_Cat, above, seems to be), it hasn't changed very significantly over the years (up until the last time anyone cared to keep close track, at least), and has even risen dramatically from one year to the next in some recent years. It's just that they're
also releasing so many other, more recent games that the "classic" releases (and I use that term as loosely in this case as GOG and the publishers do) can kinda get drowned out. Same number, lower proportion.
(It also doesn't help that one or two of the dedicated "old game" publishers that have been releasing stuff here lately -- Ziggurat, for example -- tend to like to dump as many titles into the store at once as GOG will let them. This means that they might release something like two dozen games in two or three months, but these will be released in bulk: maybe 3-8 games on a given a release day, but with only perhaps 4-6 such "release" news posts spread out over that several-weeks-long period, hurting visibility for these releases somewhat.)
A couple of my more in-depth explanations of this perceived phenomenon (the first linked post is rather old now, but mostly still true):
Why GOG releases old games so slowly GOG and competition in the "old games" market And, for good measure,
here's a hacky way to filter the store catalogue by release year (not specific years, just preset ranges). The results still won't be comprehensive -- it won't show remasters or re-releases where the date given on the product page is the re-release date instead of the original one, for example -- but it's a starting point in your search for recent "classic" releases. :)
example: games from before 2010, sorted by date added to the store (newest first)