Armstrong, who was part of the 1990 grand slam-winning side, as well as leading his compatriots to the championship in 1999, was scathing about the manner of the back-to-back defeats against Ireland and England, which have left the Scots at the bottom of the table.
Pressed to pinpoint positives from these matches, Armstrong told Herald Sport: "You're asking the wrong man. I'm not even sure he [Johnson] has got the respect of the players any more. I can't understand a lot of the selection decisions he has made and nothing is clicking at the moment. Guys such as Kelly Brown and Richie Gray are being picked for one game, then ditched for the next, and the chopping and changing doesn't make any sense. I feel sorry for some of these lads, but I feel even more sorry for the supporters.
"It doesn't give me any pleasure to say this. It's exactly the opposite. It saddens me, it really does, because anybody who pulls on the Scottish jersey knows how much it means. You are not just playing for yourself; you are playing for your country and all those fans who pay good money to watch you.
"I don't know if the incoming coach [New Zealand's Vern Cotter] has any input into what is going on at the moment, but he can't be happy with the performances and I am not that optimistic things will get any better. We have to go to Italy next and they stood up to the French scrum in Paris a lot better than we have managed in the two matches so far. It is very, very hard to find positives."
Armstrong's downbeat mood was echoed by his former team-mate, George Graham, who said he was concerned at the dearth of ideas or even a mastery of basic skills, which he had witnessed throughout the opening brace of fixtures.
"The boys didn't look as if they are having any fun or enjoyment from what they are doing; there wasn't much sign that they had a Plan B; and they are short of confidence. It doesn't add up to a great combination," said the former Scotland prop.
"But we have to be careful about being too critical in these situations. Some people have claimed the Scottish boys have lost their pride and passion, but that is rubbish. They are trying their hardest but it isn't happening for them. I think the lads have to remember that rugby is supposed to be fun and they should go out and express themselves.
"Things can change quickly in sport. Let's not forget, either, that England played really well against us and the Scots got hit with the backlash from them losing in Paris. What we can't keep doing is bringing in lads then discarding them, and constantly changing the side. We have to show a bit of faith in some of the youngsters and let them develop."
Graham was particularly irritated by the notion that Stuart Hogg, the Glasgow full-back, should be switched to the stand-off berth at the expense of Duncan Weir in Italy.
"There is a tendency for us to build players up then knock them down and, yes, Duncan didn't have his best match against England. But how many games has Hoggy played for Glasgow at No.10 this season? Or last season? You can't just fling people into different positions at a few days' notice and expect them to hit the ground running," said Graham.
"I would stick with Duncan for Italy and tell him, 'Don't be scared to have a go'.
"I know he kicked away a lot of possession, but he doesn't do that at Glasgow, so was he acting on orders and sticking to the game plan?"
Which brings us back to the coach.