I've been alternating GT7 with Ark Survival Evolved (because who doesn't want a pet Triceratops?).
When I've actually been playing GT7 lately, I've tried to do things a little different, too. Grinding for credits is a complete farce given the prices of the Hagerty cars, and it'll only get worse, so I've all but given up on owning them. PD encourages us to collect cars and then makes it a full-time job to do so. No thanks.
So, what I've been doing is buying the cheaper cars and modifying them, and then using them in some of the shorter, easier races (as opposed to time trial mode) to set them up. For example, I bought a 1965 Mini Cooper, and shoehorned the Civic Type R F20 engine into it for shiggles. I then ran the 25,000Cr. 2 lap race at the Catalunya short circuit a few times while I dialled in the suspension and LSD settings. I hate Catalunya, but the short circuit is actually pretty good. Once I'd done the race 3 or 4 times, I was fairly happy with my set-up changes, and had earned back some of the money spent buying tuning parts.
I then took it to the Hyper car parade at Trial mountain, which was pretty hilarious. Doing this, I had a lot more fun this way than doing the Sardegna race over and over with my Gr.1 Tomahawk.
With american cars, I test them at Watkins Glen short circuit, and japanese cars go to Autopolis clubman event. This way, I get a bit more variation than with grinding, and I get to drive the cars I want, instead of the race cars I don't enjoy. My favourite car lately has been the Corvette C4 ZR-1, which I've built into a replica of the Doug Rippie car that raced (and retired after 20 laps) at the 1995 Le Mans in the GT1 class. 550bhp, 1225kg, RH tyres, and a stable set-up to make it feel planted.
Alternatively you can try tuning up some road cars to beat the Sardegna event. Winning with a VR-swapped Delta with 900bhp was kinda funny, or the fully tuned Camaro ZL1.
Another thing to try is tuning up some cars to a similar performance level, and race against them in a Custom race. I made my own little rallycross event recently.