Because we're talking about the situation now Marcos, not two decades ago
How much money would you put on any team outside of Barca and Madrid winning the league in the next 5 years? In fact feck that, how much that 3rd place will be within 10 points of either of them?
Liverpool and Newcastle could and perhaps should have won the league during that time period you cited. Competitiveness doesn't boil down to who wins it in the end, it's who's fighting for the title until the end
We're actually talking 2008 - which was last time Barcelona dropped out of the top 2.
How accurately can we forecast the future? When we saw Chelsea win their first PL, people were predicting it'd be years before they could be caught - it was two years. When people were admiring Ronaldo and the Galacticos at OT how many people would have predicted that the 2003 La Liga was basically the only thing Ronaldo would win in Spain?
I do think Spanish football has a big problem on its hands - you only have to look at the empty stadia (even Madrid and Barca experience this at aways) to see that even the lower entrance fees are too much for a country with 20% unemployment
However I also think that we're witnessing a freak situation in the football cycle. Had Barcelona been able to coast to last year's title (and this one) I don't think we'd have seen the outrageous points gap - they'd have rested players before CL games for example, and everyone would have nodded politely and said, "three in a row - well, they are the best." It's the simultaneous strength (and hunger) of the big two that makes it so extreme and that won't go on forever. Money or not, that's not how football works.
If the contenders had organised better maybe they could have put forward an offer that the small clubs could have gone for (Barca and Madrid have basically decided to keep the small clubs afloat). Instead they focused on how they (as individual clubs - even the group couldn't sound united) could get more money - understandable, but tactically naive.