Dortmund didn't really have players with any buyouts since Götze. Halaand is really the first one and we all know that Halaand (Raiola) were only willing to do a deal with a buyout clause, I mean the rumors say that's actually the reason why United didn't get him (weren't willing to agree to it). Halaands bo is also pretty high, it's still rumored to be 75m € in 2022 so not bad considering the circumstances.
You also need to keep in mind that players in Spain are required by law to all have a buyout clause which is the reason why you see some of those ridiculous BO clauses of several hundred million for pretty average players or just highly rated talents.
In regards to Felix/ambitious transfer targets... it's simply a different philosophy in regards to finances/risks. In case of Atletico their deals often involves other parties who get a proportion of any future sales. In the past Atletico "bought" players and didn't even own them so any money that came from those didn't even got to Atletico.
Falcao was a famous example of this:
https://www.sbnation.com/soccer/2013/6/13/4399382/falcao-monaco-third-party-ownership
You should also remember that Dortmund did refuse to sell players in the past because of their ambition, that's why they lost a player like Lewandowski on a free transfer instead of selling him earlier. I also don't need to tell any United fan what happened in regards to Sancho and their refusal to sell for less than a stellar price.
I'd say Götze is really the one case where they didn't get what they really wanted but let's remember that his contract was signed at a time when Dortmund was still feeling the impact of their debts and 37m € was still a huge amount of money in 2013 (Hazard went for 35m € to Chelsea just one year earlier).
I mean Suarez is comparable to getting back Hummels from Bayern and Sanchez doesn't earn more at Atletico than Reus at Dortmund. I'm also sure Dortmund would have paid Klopp pretty much what he wanted but in the end it's just not only about money either.
There is certainly an argument to be made that Dortmund should have done better in the league and internationally in the last few years but that's imo down to the difference between managers at the respective clubs. Dortmund under Klopp was simply a different beast (Dortmund actually managed to defend the title in 2012, let's not forget that) and even Tuchel's Dortmund was a lot closer to Simeone's Atleitco. You can also certainly make an argument that having Barca AND Real as national competition makes it harder but one needs to consider that we simply haven't had a bad season in any season since Dortmund title. Even our worst season since 12/13 still had us at 78 points after 34 games in 18/19. Klopp's Dortmund won its titles with 75 and 81 points (which was a new points record at the time and Klopp infamously said it might be one for the ages...).
In Spain Atletico has been behind Barca in every single season since their title in 2013/2014 so even without Real it would have never been enough to win the title. 2013/2014 was an exceptional three way races between the three (and Barca/Real did end up with an average points total that is the exact same as Bayern's worst season since 11/12) but that is really the exception, usually Barca is on a national level also very dominant which is why even Real only won 3 titles compared to Dortmund's 2 since 08/09!
Looking at the current season even a Barca in crises mode seems to be more likely to end up as 2nd behind Atletico than Real.
I mean "ambition" here just means to take huge financial risks and really ignores Dortmund's past. Dortmund nearly went brankrupt in the early 2000s because they tried to force things through extreme investments into players and their wages because they wanted to compete with Bayern. The club was lucky to find Klopp and get back to its feet or else they'd be where Hamburg is now. If you aren't from Germany/don't follow german football it's maybe hard to understand how much it impacted Dortmund but it was a really dire situation (and it is not a case where "being bankrupt" is just hyperbolic language, it could have ended like with Leeds in the EPL).
The same is by the way true for Atleitco and Simeone. Look where Deportivo La Coruna is today or what Valencia's investor did to the club. Atletico gambled and won, good for them but it can also change at any time (like I said they have a mountain of debt) and Dortmund at least managed to stabilise the club at a high competitive level after Klopp so they at least found a sustainable way to be where they are. Will Atleitco manage to do the same if Simeone is gone?
Let me put it this way: If Dortmund had been more cautious in the early 2000s they might have been amongst the very, very top clubs today but instead they crashed and missed nearly a decade of financial development at a time where clubs could create enormous growth.
So maybe in the here and now Atletico's philosophy might give them a bit more success though I think that's really down to just Simeone but Dortmund has a much better foundation for sustaining it in the long term. They actually have a chance to develop into a top tier club but for that they need consistency and more time to develop the club. Bayern needed decades to achieve its status in world football, without sheikh you don't become an elite football club in just a couple of years.
