Engineer and architect of large enterprise products here (2 million line Java/C# behemoths that do all sorts of weird and complicated financial shit).

Reality is actually as follows. Not joking I've done this job for 15 years and worked with several large companies including one you mention. Perhaps your experience is in the 1% of "enterprise" companies who have clue but this by far is the majority:

Bold statement here: 99% of the use cases of all these patterns are totally pointless and a waste of money and time. The add nothing to the product, they increase complexity, decrease performance. It's cheaper and more reliable to chop your product up and write each chunk in whatever separately with no official architectural pattern usage system-wide.

Typically in the real world, you're going to end up with:

1. Literally tonnes of DI/IoC code and configuration for an application with an entirely static configuration. This is either in XML or DSL form using builder patterns. Consumes 30 seconds or more to start the application up every time. Aggregate over 50 developers is 16 hours a day pissed out of the window.

2. Proxies for anaemic domain models that are fully exposed. Consumes 30 seconds to generate proxies that do sod all. Aggregate over 50 developers is 16 hours a day pissed out of the window.

3. Leaky broken abstractions everywhere actually destroying the entire point of the abstractions. Makes refactoring impossible and maintenance hell. It's better in some cases that they are not even there and that basic savvy is used over COTS patterns.

4. Acres of copy pasta. Why bother to write a generic implementation when you can copy the interface 50 times and change the types by hand?

5. Patternitis. So we need to use the BUILDER pattern to write the query to connect to the DOMAIN REPOSITORY for the AGGREGATE to call the CODE GENERATOR that fires up the ADAPTER to generate the SQL using the VISITOR PATTERN which farts out some SQL to the database PROVIDER (and a 90 layer stack dump when it shits itself). This is inevitably used in one small corner while everyone in the rest of the system hits a wall in the abstraction and says "fuck it" and writes SQL straight up and skips the layers of pain and because there are no code reviews (because people are all sitting there waiting for their containers to start up whilst posting cats on Facebook).

LINE 10 (remember this)

These things are never rewritten or refactored. They slowly evolve into a behemoth ball of mud which collapses under its own weight to the detriment of customers, a team of enterprise architects (usually from ThoughtWorks etc) usually appear at this point then attempt to sell outsourcing services who will "fix all the shit" for a tiny fee, leave a 200 page powerpoint (with black pages just to fuck your printer up). The company struggles on for a few years and is saved at the last minute by a buy out by a company at an early stage of the cycle who slowly port all the customers and buggy shit to their product platform. Then the team either dissolve and knowledge is lost or they take a cash sum from the sale and start up some ball of shit company that does the same again.

GOTO 10.

That's enterprise 101 because the people that have been hit by the clue sticks know better than to subject themselves to this and do work in SF and SV and London. Me: I'm a masochistic crazy person who wonders every day why I don't just go and write web sites for half the cash or flip burgers because it's less painful.