Sometimes, junior developers look down on me because I don't know the keywords of the newest hyped-up framework from memory. You could call it technical debt that I keep using mostly old and boring technology.
Or you could call it "mind-blowing cost savings by reducing technical risks" and let management send you a bonus payment ;) Despite what the React docs suggest, an SPA is usually not the best architecture.
Wait until their code is so bad that they are spending 100% of their time just fixing bugs, while you are maintaining critical code in production with zero bugs, working 100% on new features. And then politely ask them if they still believe what they claimed back then or whether they have learned something from their choices :)
Unfortunately they usually leave before their code hits 100% crappiness, leaving a mess for people to take over. I have seen this so many times that it stopped being funny a long time ago. Which is why I only hire experienced developers.