FM7 was easy to get credits in as long as you didn't try to buy a new supercar for every race. There were also some easy tricks to make credits fast using the "rewards" things or whatever they call it where you can choose between a prize car, driver gear or mod pack.
The career was still lame but it tried a little more than previous ones, with divisions now instead of just class based racing. You could also change the career mode races to "long" or whatever it was called and they were like 3x longer or something, so it gave it more of a natural feel instead of the normal "divebomb turn 1 to get first or restart" nonsense from previous ones. AI is still garbage though so even with the longer races, wasn't much fun but then that's speaking as someone who primarily races in organized leagues so I'm used to racing against people so by comparison AI is pretty much always terrible.
FM7's "free play" mode is pretty customizable, with a bunch of restrictions and controls, it's almost like FM4 online private lobbies except you can't manually assign AI cars like you could back then.
Overall it's a good game in most areas really but rose tinted glasses for FM4 and the troubled launch taint FM7 for many people. The main issue with the game really is that the racing is shallow with no drafting, no tire strategy, a crap tire temperature model, and basically no progressive damage other than engine and transmission. It makes every race a maximum-attack, flat out sprint race with no need for strategy or car management or using your brain really, and coupled with the crash-your-way-to-the-front career mode (because lets face it, most people don't change the races to "long"), it teaches everyone to be hyper aggressive all the time and makes random hoppers kinda terrible to race in.
FM8 will be interesting because the tire strategy and fuel strategy stuff is going to be a complete culture shock for the vast majority of Forza players, and unless T10 dumb it down so far that it's inconsequential (which I wouldn't put past them), it should make early days in the game hilarious as people are gonna constantly be screwing up strategies and stuff. Should be tons of zero IQ racing and I'm excited for it.