I was around back in those days and traditional 9's had a lot of success. Vieri, Inzaghi, Salas, Zamorano, Kluivert, Batistuta, Delvechio, Bierhoff, Signori, Shevchenko.
I mean Ronaldo wasn't the most successful striker of that era even when he was fit. 2 cup with Barca, 1 cup with PSV, 1 cup with Inter, 1 league and 1 cup with Real, 1 world cup. With Haaland pace and finishing he would of been insane in that era, like Vieri on steroids
Weird view.
His PSV time was against LVG's Ajax, having a golden generation, who won CL, and made another CL final. It's like asking why Haaland didn't win Bundesliga with Dortmund, nor why not outscoring Lewandowski. Ronaldo missed a huge chunk of his second season due to his first serious knee injury, too.
That Barcelona went through a transition and in identity crisis with Sir Bobby Robson before LVG first stint. Real Madrid happened to have Capello who at the time regarded one of elite managers in his peak. That Real Madrid may not be Galaticos, but they were on par with Barcelona; and they didn't have European duty because they stank the previous season. Barcelona issue was not outscoring. It was that their defense was significantly weaker. Barcelona lost the title to Real Madrid for only 2 points. It speaks volume of Ronaldo individual brilliance as a player, by dragging his team as far as they could, challenging Capello's Real Madrid, regarded as a much superior manager than Sir Bobby Robson.
Serie A of the 90s was a Super league, even when Juventus was supposed to be dominant.
I am not sure what you meant by a lot of success, when you listed Signori who only top flight success is Intertoto Cup. Yes he's a monstrous goal scorer, but your argument would be all over the place to use goal scorer individual tally to define success because in his first season in Netherland, Ronaldo way way outscored Kluivert, who played for a stronger (dominant) team. In the second season, despite the injury, Ronaldo was only about handful of goals behind Kluivert!!! Kluivert flopped when he moved to Serie A, and quickly shipped out to Barcelona after only a season to play for LVG!!! Kluivert boasted trophies but his goal scoring tally per season at Barcelona again was below fat version Ronaldo in La Liga...
Delvecchio is neither as consistent scorer, nor that really decorated. Won one Serie A and Italian Super Cup but it happened to be with when Batistuta arrived. That Roma squad was tasty (Totti, Cafu, Emerson, Samuel to name a few other notable great players), and Capello (elite manager at the time) was more the driving force for AS Roma success.
Outside success with Roma, Batistuta trophy count is very unimpressive hence why he needed to eventually move to Roma. He's no doubt an elite forward with consistent high scoring rate in toughest league at the time. However, Ronaldo first season at Inter when he's fit, he reached about same range of goal, Batistuta's best season could offer!
Bierhoff legend was based on him (at Udinese), outscoring Ronaldo first season at Inter. However, throughout his career, even when he's part of Milan team who won Serie A, he's not as consistent 20 goal Serie A scorer in same tier as Signori, Batistuta, Shevchenko. His only success is again moving to Milan and won Serie A. His overall club career success was even less decorated than Batistuta's.
Salas boast trophies being at the right clubs at the right time, but he and Zamorano were not that prolific in Serie A. Zamorano was as successful at Inter as Ronaldo!!! His overall success in Europe is about the same Ronaldo's too, but young fit Ronaldo way way outscored Zamorano's best seasons.
Vieri became a consistent scorer for few seasons during early 2000, but before that even when he was leading Italy NT line, he's not consistent posting great numbers at the clubs. His success with Juventus and Lazio were the clubs power (other great players, and managers) than Vieri contribution. Haaland maybe faster, but he's not on the same top tier speedster like Ronaldo. Vieri was not slow. He's not only a box attacker. He's quite confident with his speed and not shy to have a go in foot race against defender. Haaland maybe Vieri on steroid, but he's not from different world faster than the younger Vieri.
Inzaghi was not always a starter. He's more like Chicharito that some seasons when he did well, he started a lot but in other seasons, more well rounded forwards would be preferred to lead the line. Again, another case of being at the right clubs at the right time.
Only Shevchenko stood out with both trophies, and consistent scoring record. However, he's only more decorated than Batistuta due to Champions League triumph. Else, he's less successful than Inzaghi's trophy count for Milan, despite Shevchenko's more prominence role at Milan.
Weah's worth a special mention. Despite not a prolific scorer, he had huge influence especially to help Milan fighting against Juventus' emerging dominance. Only African who won Ballon D'Or for a reason. He boasted trophies to go with his influence, but great scoring record is not what he can boast about.