Yes, the thing Salesforce are good at, and is little understood here, is that they've kept their platform online for 27 years so far. Its constantly evolving, three upgrades per year, but changes that require customers to change their customisations are rare, and when they happen they are communicated at least a year in advance. Approx 150,000 tenants, all with different configurations and some so heavily customized that they are effectively unique apps. Salesforce keeps them all online and evolving. In those 27 years there hasnt been a 'lets trash this and rewrite from scratch' and there hasn't been a 'you must migrate your data to our new platform, we're closing the old one'. They've just evolved it while running. They must have got some things very right in the original architecture to be able to do that.
One thing that I find interesting is that they launched their platform language Apex (a sortof subset of Java) in 2007 when TDD was the hot new thing, so TDD is baked into the platform - your Apex code must have at least 75% test coverage, and the tests must pass, before you are allowed to deploy to prod.
They leverage that test coverage when they are upgrading the platform - they have an internal process called The Hammer where they run all customer-created tests against customers own unique configs on the current platform and then again on the next version of the platform to see if any customer tests are being broken. Look it up, its really interesting.