Well yeah - it is. But specially with coil there is actually a lore-reason why it is locked out - you might not care about lore&story and only about killing stuff and getting your loot. But I do - and I assume a lot of other people do aswell. Clearing all of that stuff today is a lot easier than it was back in the days it was "fresh". My point stands: You're not skipping chapters of a book or parts of a film. Coil is telling you a story and there will be references back to earlier turns... oh wait... you havent seen that? I wouldnt even call that lock out - its progression... in story and in mechanics aswell.
Also for a fresh-level50 or someone who just came back into the game those lock outs might be some sort of guidance - I've seen people being overwhelmed by all those dungeons they've got access to in the blink of an eye - having something they can kinda look forward to and work their way up isnt a bad thing at all...