Japan has a highly developed industry, including a very successful car industry. Japan has a long history of building aircraft, they produce their own military jets, they build their own orbital rockets and satellites. Clearly they country is capable.
And yet it appears that post-WW2 Japan has only build two indigenous airliners, NAMC YS-11 in the sixties, and then MRJ now (and MRJ is still being developed).
Just a quick moderation reminder to anyone considering answering here: even though the question is posed in the present-tense, kindly respect the sub's 20-year rule against discussing current events by limiting answers to events/conditions occurring prior to 1998 only. Thanks