The team was in decline already when Ronaldo came. Khedira was done, our midfield was Pjanic and Matuidi, and a bunch of mediocrity. Buffon was leaving, Barza too. We still had Chiellini, and Benatia was a good starter, but the next in line was Rugani. Licht was gone and we were left with De Sciglio (Cuads wasn't a fullback yet). On the other side only Alex Sandro. Higuain was in big decline (as the next seasons showed), Dybala was difficult to build around (lopsided 433/442s), D. Costa came off a great season but was injury prone and Berna was a flop. We still had a pretty good Mandzukic tho.
So Ronaldo walked in on this, and our summer mercato wasn't that good. Emre Can as the only midfield signing (for free but actually for 16M lol), we brought back Bonucci who in the end cost us Benatia, so we were left with Rugani playing the biggest CL ties. Spinazzola and Cancelo were great additions but we needed a starting mid badly.
We went all in with Ronaldo, but didn't have enough chips for that. And our chips got fewer and fewer as years passed so it didn't work out. Our first year with him was our only shot really. Had that team stayed healthy, we were I think the favorites with Tottenham, Barcelona and Liverpool, of which neither looked impressive