I'll have to disagree a bit on the "You don't need to design internal tools well" argument.
I get the point the OP is trying to make, and certainly agree up to a point, especially when you are comparing to an external UI. Obviously in most cases, your customer facing UI should be much more well designed compared to your internal tools. Of course.
... but, this argument only makes sense when there is a trade off like this to be had. In many larger organizations, (which tend to have more internal tools), it is not the same teams which build the external and internal tools. And the larger your organization, the more (internal) customers you have and the more married to these tools their work is.
Just anecdotally, if the tools we built for the internal customers for my team were not well designed (as in well thought through), it will definitely piss folks off - because many folks use these tools throughout the day. Many internal users spend > 90% of their time on a handful of tools. Looking great is optional, but looking good, and working great in not. I wish I could give more concrete examples, but in many of our internal tools I have found that a few lines of CSS could make a a difference of night and day.
Not necessarily against the point OP is making, but just wanted to flush it out in more detail.
I think OP isn't against well-designed internal tools, just against requiring the fine presentation and theming that custom CSS now enables. Their point becomes clear when they say that devs can just slap a framwork like Bootstrap on internal tools' presentation and call it a day, no CSS required.
I get the point the OP is trying to make, and certainly agree up to a point, especially when you are comparing to an external UI. Obviously in most cases, your customer facing UI should be much more well designed compared to your internal tools. Of course.
... but, this argument only makes sense when there is a trade off like this to be had. In many larger organizations, (which tend to have more internal tools), it is not the same teams which build the external and internal tools. And the larger your organization, the more (internal) customers you have and the more married to these tools their work is.
Just anecdotally, if the tools we built for the internal customers for my team were not well designed (as in well thought through), it will definitely piss folks off - because many folks use these tools throughout the day. Many internal users spend > 90% of their time on a handful of tools. Looking great is optional, but looking good, and working great in not. I wish I could give more concrete examples, but in many of our internal tools I have found that a few lines of CSS could make a a difference of night and day.
Not necessarily against the point OP is making, but just wanted to flush it out in more detail.