About the grinding, I'm finding hard to realize the problem...
Because the payouts are still similar or higher than previous GT titles. A clean race at Ficherman's still gets you 45000 cr in less than 3:30 minutes, not very different from 52000cr in about the same time in NASCAR at Motegi in GT6, considered the fastest way to grind in GT6, not considering glitches. And the Jaguar XJ13 still costed 20 millions. Most similar cars have similar prices or are cheaper in GT7. Don't make go back to GT3, considered by many the best title of the series, to talk about how much painful grinding can be!
But, as there was no microtransactions, that wasn't a problem on those days, I guess...
Sure there are invitation cards that expire, you loose the opportunity to buy a certain car.
Wrong was if it was like... a Gr. 4 or a Gr. 3 car cost millions of credits, we must grind for days just to buy a car to use on a Daily Race C. Grinding Fisherman's for a little over half an hour you grind money to buy a Gr. 3 of you like. At Blue Moon Bay in GT Sport you could do it faster, but not so much faster.
The only problem to me with grinding is the lack of deep in terms of races and championships for top end cars. Surely those races will pay more than the current races available.
But the problem seems to be you can't buy the whole bunch of supercars and hypercars in the game after a week since the release of the game.