Let's put this into a test setup: 20 meters distance (120 penetration vs 180 armor), flat terrain, only frontal shots possible, only actual hits counting. We count 50 hits, assuming that the players in the discussion above would have their last roughly 50 shots in mind when thinking about the engagements. We do 20 tests to form each player's experience.
Basic statistics tells us that the real penetration chance is 66.7%, meaning 50*(120/180) = 33.33 shots should penetrate with a standard deviation of 3.33 shots (10% of the mean in our case). This means that almost one third of the players discussing will have had the Sherman penetrate less than 30 times or more than ~37 times. One player will have had the experience of the Sherman hitting less than 27 times or more than 40 times and probably be screeching about the trash Sherman or saying it were OP.
Even if all discussion was fully rational (good luck with that), players will regularly report a penetration chance anywhere between less than 60-75%.
This is human nature - remembering anything that seems out of the ordinary. I once had 5 shock troops killed by a single Panzershrek shot because they walked around a corner and were stacked on each other when it hit. Clearly the Panzershrek should've been nerfed! I just couldn't motivate myself to start a thread over it so justice wasn't served.....
Normal people (meaning everyone that didn't have to take a statistics to get their degree) often underestimate how common "uncommon" results are. Take the normal heads or tails. Theoretically it's 50/50. Would you ever expect to roll 9 tails in a row? You can simulate this in Excel by putting "=rand()" in cell A1 and "=round(A1,0)" in cell B1, copy that down 99 cells. Rand will recalculate every time you hit F9. If my Sherman had a 50/50 chance of penetrating a Tiger and I fired 100 shots, I would've got 9 bounces in a row on my third recalculation. Streaks of 9 are somewhat uncommon, but 5-7 are really common.
Excel will also simulate your test. Replace the Round function with "=IF(B1>0.667,1,0)" and add "=COUNTIF(B1:B100,1)" to any cell near the top. Hit F9 a bunch of times and see how bad or good your Sherman is. In short, Excel is OP.
The two counter arguments I'd make against just looking at the numbers in Excel are about the effect of alpha damage and time to kill being irrelevant. In a RTS, alpha damage has an outsized effect because it greatly increases the risk of losing a squad. That was a lot of the problem with the old IS2. It seemed to go miss, miss, wipe on squads a lot, but sometimes it started with the wipe. The other problem is that people like to argue about the time to kill. I've seen multiple comparisons where people are comparing TTK times in the 20-40 seconds and trying to use that to make a point. In an actual game, 20 seconds may as well be an eternity, as nobody has reactions that are that slow. The bazooka was once nerfed because Relic thought the TTK was too short.
Back to original topic - Based on how often the commanders are picked, it doesn't seem like the majority of the top 200 think the IS2 is trash. It's just that the commanders have fallen into the "B" tier. Trash is more like Conscript Support, Tank Hunters, any Partisan commander, etc.