I guess it shows that there so many issues to consider both software and hardware wise that it's not simply changing a few lines of code and TA-DA, it works. It might even be on my end where I need a different codec or something. But I can watch the red line grow, it changes to carousel pic #2 with a white space for the image. the forward/back controls on the sides work and all, just no images except for the first one.
For a public site facing rollout there are a ton of things to check.
You have different web browsers, different versions of each web browsers. Different operating systems (which constrain some web browser usage).
You then get into all of that all over again with mobile devices (phones and tablets).
For the user experience you must consider usability considerations, user interface considerations, color/scheme considerations, language considerations, and timezone locale considerations.
This is technically a migration so you have to consider the old version of all user experience stuff vs the new version that is coming when comparing aspects and features that are supposed to be "apples to apples".
Then there is the whole back end of things you a user never sees.
With the migration from old to knew you must make all the old data work with the new site WITHOUT losing the data or corrupting it.
Depending on the how big/serious the migration is you may be moving to all new hardware/software infrastructure which means potential architectural and system changes.
Then you throw on top all of the NEW stuff being added that has to be vetted and how it jives with the new user experience that is attempted to be provided that would now be an "apples to oranges" comparison with the old site.
Now throw in performance testing and tuning to make sure it all runs in acceptable timings (usually sub 3 second responses and many things faster than that).
Finally, you have to handle ALL of that and ensure it is accounted for so well at all levels that you can consistently make the migration happen without it missing things, changing things, or it all blowing up without having unplanned downtime/outtages that cost you dollars and end user confidence.
There are no regulations or end user finances to impact with this migration which makes it a really low impact and seriousness to the world BUT it does impact the jobs and dollars of everyone who runs the site as a business so it is very serious to them and to the community that uses it non-stop daily.
That is WAY more info than you probably care for but it may help to understand a very very very simplified version of what does/can go on with something like the current site change. I hope it sheds enough light on things that people understand that things are being handled quite gracefully with any show stopping issues. It look focus right now is on the more "serious" issues and then the desired changes that are being encountered right now