The MK7 generation, and particularly the 7.5 (facelift) was a particularly loved iteration of the GTI. It did everything really well and the looks inside and out were on the money. A 7.5 GTI is still a really good looking car in the right spec!
The MK8 got a bit of a lukewarm reception... the looks aren't quite as good (to most people's eyes anyway) and VW went "full digital", replacing physical buttons with touch screens and haptic buttons. The software was very ill thought out, many cars suffering from bugs, cars plagued with bings and bongs and dealers clueless about fixing them. There's probably not many MK8's that haven't had at least one new steering wheel fitted...
I think a lot of the negativity around them comes from YouTubers (as Fred alluded to above), who have the car for 20 minutes and b!tch and moan about the steering buttons or the touchscreen. But if you own the car and get used to it over a few weeks, these YouTuber issues are non-issues.
I had a MK8 Clubsport for 3 years and it was largely a pleasure to own, I may have been lucky but I didn't have any of the software issues. It was probably the most reliable VW I've owned, as I don't think I was ever back to the dealers for warranty work.
I recently replaced it with a new 8.5 and I'm especially delighted with the new car. I think they've really nailed it with this one. The iffy styling elements of the MK8 are much more resolved in the new car imo. And the new software / infotainment screen is on another planet in terms of usability, ease of use, etc.
In terms of desirable options, it's very much personal choice, but I think most agree that the standard 18" wheels are absolutely gash, so you gotta upgrade those to one of the 19" options. That would be my main dealbreaker anyway.
After that, I'd strongly recommend looking for a car with DCC (adaptive chassis). It does make a big difference.
In my new car I opted for the pano roof and I love it! Such a cool feature, delighted I spec'd it.