My D90 makes it, but my D100 is disappointed !
Yes,, I think the era where the digital camera was a suitable replacement for the beloved film was when the D90 was released. It is only a stop less low light for any given signal to noise ratio compared with any other Dx camera since. The cameras that had essentially "ISO'less" noise character began with that camera and the followup D7000 made that linear plot of noise to ISO rule straight which meant if one lowered ISO a stop resulting in an underexposed image, and boosted in post processing by a stop would be virtually identical to an image exposed 1 stop higher and properly exposed. That is when read noise is lower than A/D + analog amplification noise. Canon shooters could not do that but Nikon owners could boost shadows up to 5-6 stops without a lot of a banding and column noise or loss of color. I would say the turning point where Digital had less downside than film was the D90. Every company since 2008 has had easily good enough performance that features had to be added to entice upgrading because of photographic performance plateaued and the changes were small incremental advances that made little real-life IQ difference. The D90 also kicked off the video craze for DSLRs. The other camera that made a step jump was the D3 and D3s. The limits of image quality stopped being defined by the camera and shifted more to the user.
To add to the discussion I would suggest an excursion to the nearest fine art gallery with top regarded art and encourage to see art as a compositional artform, and how the artists used cues from lighting to and composition to tell a story or show much more than just brush strokes.
Other aids to improving quickly that does not involve getting a new camera is going to workshops or going to shoot with an advanced photographer whose work you admire.
And if the itch is to buy something.....#1 return on investment and step up is lighting, any sort of lighting you have control of will supercharge your images. I hear the complaint from those stuck in a creative rut that they "only shoot natural light, I don't like the flash look".
ALL light is natural and that is all we have to see with. We do not see objects, we see reflections of light and selective absorption by the frequency of light. Our brain uses that to infer what the reflecting surface was. Anytime you can help tell your story with more control of the information, you have expanded your artistic vocabulary. The complaint about the "flash look"is they object to the poor use of light without realizing that they are only a few hours of practice away from turning "flash look" shots into "hang over the mantle-worthly portraits" It is hard to find a great photo where photographer influenced light was not a key. Every photo was seen on the cover of a magazine, or ad had augmented light, even those shots of people on the beach used controlled or augmented light. No one noticed bad light because it was used well....but it WAS used.
A simple homemade reflector can change everything, a $3 shoot of white foam core can wonders in portraiture, indoors or out. A homemade scrim on that beach shot makes the difference between a glossy magazine cover shot and a hard mid-day raccoon eye snapshot that is tossed out. A few cheap Chinese flash units with RF controller, cheaper than any lens, can put studio quality in your camera bag.
If someone is upgrading camera bodies before upgrading lighting options that are missing the boat and wasting money. ALL sorts of photography benefit from more or better quality of light, even nature photography where the eye does not expect augmented light was used to capture the great shots out there.
A great camera club activity is renting a studio for 2-3 hours and a makeup artist hired. Or a joint construction project of making a number of handmade modifiers.
For those interested in model photography, one of the hardest crafts to master is posing, it is a skill and makes a lot of difference in the results particularly if your subjects are friends or family, amateurs.
Having the club hire a pro model for a few hours and having them teach you how to work with models. A good model has a lot to teach a photographer who is beginning and finding one who is interested in helping potential employers learn posing can be very instructive. 1 hour with a pro male or female model trumps any books on the subject of posing. Even if only doing head shops or head and shoulder shots, learning posing makes a great difference between a selfie and an image of art. Female models are more versatile generally with a broader range of assignments and easier to find ones with good pro experience. As a workshop for the whole club, a lot could be learned in an hour.