I feel like I'm the only one, but I actually prefer the forehead of the week type to over the top wild designs. I'm used to it now and It just feels more like Star Trek to me.
That's the thing, though... I grew up on TOS, and though most of its "aliens" were just humans in funny clothes or painted various colors, when it did go for something more genuinely alien, it often went very far afield -- the Salt Vampire, the Gorn, the Horta, the flying parasites, Sylvia and Korob's true forms, the Companion, Andorians and Tellarites, the Mugato, the vampire cloud, the (unseen but described) true form of the Kelvans, the Melkot, the Medusans, the Tholians, the Excalbians, and the various energy creatures. And then TAS came along and continued that trend of exotic creature designs -- Arex and M'Ress, the "Beyond the Farthest Star" insectoids, the Vendorians, the Phylosians, the Kzinti, the Lactrans, Sord, Em-3-Green, the Vedala, Bem, the Dramians, Kukulkan, etc. And there were some decent attempts at exotic alien extras glimpsed in the crowd scenes of ST:TMP and TVH.
But TNG and its successors, despite having more budget and technology available for makeup, relied far more heavily on humanoids, clinging religiously to Roddenberry's reputed preference for keeping some human element visible (even though Roddenberry's direct influence on the shows was minimal after the first season of TNG). We saw hundreds of new aliens, but we had a much smaller percentage of nonhumanoids than TOS had. In TNG, for instance, leaving aside giant spacegoing creatures like the Crystalline Entity, incorporeal energy beings like the Calamarain, microscopic creatures like the "Microbrains," invisible creatures like the "Darmok" monster, nonhumanoids that are kept offscreen like the Jarada, human-disguised shapeshifters or illusion-casters like the allasomorphs and Barash, and parasites inside humanoid hosts like the "Conspiracy" aliens and the Trill, we're left basically with the Anticans, the Selay, Armus, the Sheliak, and the "Solanae." So TNG had a pretty weak track record featuring nonhumanoids that were actually seen for a significant amount of screen time. Granted, several of TOS's aliens were shapeshifters or incorporeal too, so the lists aren't that different in size, but keep in mind that TNG's list is out of 2.25 times as many episodes. The nonhumanoids are a much smaller percentage of the whole.
As for DS9, it had a bunch of elaborate "mask aliens" in the background, but they virtually never played a role in the stories, except for Morn. VGR did a bit better, as CGI tech advanced, but its aliens were still overwhelmingly humanoid. It wasn't until ENT that we started getting back to the richer mix of humanoid and nonhumanoid aliens that TOS had.
