That remained open after the 16th century due to some very special circumstances. The Dutch hated Catholics almost as much as the Japanese did, were present when Japan was still comparatively open to trade, and went out of the way to appear humble and subservient. The MacCartaney embassy will arrive at about the same time as the various Russian scares starting to kick off, which did little to make Japan open up-quite the reverse, in fact. It will alert the Japanese to the continued presence of the British fairly near their seas, but will probably achieve little else. Of particular note is Macartney's unwillingness to kowtow before the Chinese. This sort of uprightness will do him in poor stead in Japan.
The presence of yet more foreigners offering trade may slightly strengthen those Western Scholars who argued in favour of opening Japan up, but will achieve little in terms of policy.