The main gap between us and the Astros and Dodgers is that we went years without producing any supplemental talent in our minor league system, had to find expensive bandaids to keep the championship core together, and then it all kinda blew up. If you want to be pissed at the front office and the organizational approach, that's where the main issue lies. It's getting better, but it was bad for a long time. Cubs drafts by top BWAR producer:
2015: Ian Happ, 14.1, Scott Effross the only other positive contributor
2016: Davis Daniel, 0.5
2017: Keegan Thompson, 2.1
2018: Nico Hoerner, 11.6, no other major league players
2019: No major leaguers, no one particularly promising
Five years with 2 players, one of which, according to you, is 'marginal'. Not great!
The biggest free agent signing in Astros history is Carlos Lee in 2006. Altuve was their largest deal ever at $151m. Alvarez and Bregman also got large deals. All three came through the system.
Freeman's deal was smaller than Dansby Swanson's (who had the best year of all the shortstops out there last year), and is their biggest actual free agency contract in history (Betts and Kershaw signed extensions for more) (admittedly, for about 3 more days).
The player advancement infrastructure just hasn't been at all enough to match up with those teams (who are, by a decent gap, easily the best two organizations in the last 5-10 years). I think we're comfortably in the next tier, and whether or not we sign Ohtani isn't going to change my opinion on that.