The RCT1 theme also enables the status bar, stoplight open/close buttons and a few other things.
There is indeed no way to left-align the top toolbar like RCT1 did. Although I wonder if that would really work that well if you consider the resolutions OpenRCT2 tends to run in. I guess it would be easy to try by fiddling a bit on TopToolbar.cpp.
I went and looked up the thread. You completely misrepresented what IntelOrca said there. This is not okay.
For anyone interested, here is the discussion in question: https://github.com/OpenRCT2/OpenRCT2/discussions/15643
The only thing IntelOrca says is "I also think that players are more likely, going to want / use hotkeys to get to particular windows and tabs, and that the players who don't use hotkeys aren't bothered about a button to access a particular tab quicker." - emphasis is mine.
Additionally, you will notice that if new features are suggested, we will generally ask why it is needed. We have limited time after all, and every feature means extra maintenance and more things to go wrong. Many features have come with new bugs of their own or other unforeseen circumstances. Bugs that we then get flak for.