Don't worry - the Twitter web team also made this mistake. But they made it at a time when TS was popular instead of earlier when the two were equally popular.
Even well after TS was clearly the better option (as in 2022) the twitter web team opposed anything being done in Typescript like separate modules that would be a dependency of the web repo.
With how much respect I have for TS now (its close to the gold standard in several categories for me), that would be a..... frustrating setup for me these days. TS just gets so much right, and is really a pleasure to work with IMO.
Even well after TS was clearly the better option (as in 2022) the twitter web team opposed anything being done in Typescript like separate modules that would be a dependency of the web repo.
At least you recognize the better direction now.