Chelsea before (1905-2003, 98 years) and after (2003-2021, 18 years) Abramovich take over club: Leagues 1-5, Cups 3-5, UCL-s 0-1(2?), UCL finals 0-3, secondary Europe cups 2-2. I see clear progress here.
Chelsea had plenty of dumb expensive signings, and it's Roman's money which helped to cover and replace dumb (Shevchenko, Torres, Kepa, Morata, Bakayoko, Drinkwater, Batshuayi etc) without team power downgrade. Club with such expensive failed transfers and without money "insurance" pocket would either fall to great debts or to the mediocre level.
Even good academy and smart management can't help to build a super-club alone, because your young prospects, self-made stars or talented players from other clubs will prefer to join current title contenders or at least good salary payers, not to your team. Leicester and current Ajax as examples.
And you should consider prices were different back then. 30 mil in 2003 is nearly the same as 60-70 mil now. And clubs like Chelsea is one of the reasons prices skyrocketed.