I wrote my first program, at the age of 15. Nothing unusual about that one might say - but it was in 1966.
I subsequently spent a career of over 30 years in software development, all stages from analysis, through design, build, implementation and maintenance.
The rot started in the 1980s when code generators started to become popular and organisations could employ coders rather than programmers who understood the "nuts & bolts". Managements also started restricting resources for analysis, design & testing. They started to excuse finding of errors by early users by claiming it was "beta testing", even though the content of the "real world" "test" regimes was undefined so the results were unpredictable.
Over 15 years ago, when we had our own family history company, a Microsoft browser update caused problems with running our scanned book CDs. It turned out that "testing" had been totally inadequate and MS "experts" even had problems understanding that there could be anything wrong when I showed them where the error lay.
Having said that, as pointed out before, if it is only Ancestry which is exhibiting problems then it is at the Ancestry end and not the browser/OS on the client machine.
Often, slowness in serving up web pages is a result of inefficient code which is full of bloatware being used to build the programs running on the server.