I agree with this statement. I would spend more time on this forum if it were convenient to do so on a smartphone, but at the moment, reading or writing posts on the bitcointalk using a mobile device only irritates me. It seems to me that in the era of mobile devices (when almost everyone has a smartphone), in which we live, our forum simply must be adapted to these devices. This would be more convenient for both old users and could attract new ones (since not everyone will want / be able to use a laptop or PC).
Although I also agree that the mobile version isn't that convenient, I believe it has already been discussed and I don't recall it being on the to-do list. I don't find it 100% necessary, but the truth is that most people nowadays are using their smartphones a lot more frequently than their computers. Thus, I believe it's something that needs to be implemented sooner or later, nothing fancy is required, just a more smartphone friendly view of the forum. Apart from that, I don't think there's something else missing, I like its simplicity so far, can't think of any other features. The most important ones, such as 2FA has already been implemented a few years ago.