Well, you got a few factors. I'm going to try balancing brevity with accuracy because otherwise you'd fall into the syndrome where refuting an entire book requires an even longer one.

And as such, the first place to start, where many common accusations draw up, is actually the man Belton Cooper. While what Cooper wrote- the book 'Death Traps'- isn't invalid unto itself, it's his personal accounts and experiences (along with an honest to god rant about how the M4 Sherman was named as such to snub the Southern US and another rant about how Patton held back the development and deployment of the M26 Pershing even when he had absolutely zero control over it) from his time in WW2 leading a mechanic detail who's responsibility involved recovering and repairing American tanks.

The problem is that what is really a memoir is then held up as a work of serious academic rigor which then necessitates long form refutations of it's falsehoods as opposed to simply being able to hand wave away, "why would a guy who's inspecting field damage on tanks be expected to understand the cradle-to-grave nuance of international supply chains and the distribution of the M4 Sherman?" since the book rose to some prominence riding on the Law of Drama with regards to History Channel documentaries- an honest analysis of the performance of the M4 Sherman was that it performed somewhere from average to above average but that's boring so History Channel seeks out the most outlandish opinions because that sparks controversy, which feeds into drama, which gets viewership. So something like statistical analysis takes a back seat because someone recounting that time they had to pull someone's corpse out of a tank in piecemeal and wash them off the tank is better story telling than being a nerd. Incidentally, if you do want to dig into the nerd junk surrounding the Sherman, I tend to steer people to Steven Zaloga's work- he's got his master's in history and his book, "Armored Thunderbolt" is a good place to start on the subject.

Second, there were actually valid points of criticism in the tank's design. Ready Racks for munitions were still relatively new and it did lead to a problem where by early model M4 Shermans which received penetrating hits anywhere near their center of gravity were almost guaranteed to take hits to live ammo. While this would often not do anything- most propellants used in munitions was at least some what tolerant of abuse- there was always that hazard of a catastrophic run-away event that had the entire tank burn up. This was only further complicated by the fact that prior to there being strict policy, tank crews were notorious for stuffing ammo anywhere it'd fit in the things. This was actually fixed in later models- redundant ready racks were deleted when it was found that most tank engagements involved shootin' and then scootin' rather than prolonged, pitched fights (in which you could then just have someone stacking rounds from stowage)- and later models had improved armor.

American war planners also made a conscious decision to withhold specialized gun rounds from the 75mm and 76mm guns- armor piercing capped ballistic cap (APCBC) for the 75mm and HVAP for the 76mm respectively- for the sake of resources- the tungsten used in HVAP was also what machining tools were made from, while the APCBC's development had stalled and wasn't given much priority- and in general they famously underestimated the number of panthers Germany would field in western Europe.

Third is what I'm going to call a cascading bias. Because tank crews were understandably dealing with fear- and indeed US training and propaganda was used to teach American soldiers to fear German tanks- they'd inevitably have stories of dealing with Nazi tanks. This was only further compounded by the reputation of German tanks- tons of accounts erroneously talk about encountering 'Tigers' by American soldiers when in reality there were scant few instances where the Americans would have encountered them. This aggregation of anecdotes from people who were understandably fearing for their lives along side reasonable observations that the 75mm gun on early model M4 Shermans had been outclassed by '44 lead to the misunderstanding that Shermans were functionally useless. This had a number of problems, not the least of which being that tank on tank engagements were rare. Most tanks were actually destroyed by infantry operated ordinance (so, everything from land mines and infantry portable weapons like AT rifles or bazookas to AT-guns and field artillery) rather than another tank because it's understandably easier to conceal a stationary gun in some foliage, or to just hide a guy with a panzerfaust in a foxhole than it is to....hide a tank. Tanks are kind of hard to miss, and in case you were at risk of doing that, their engines are loud, and in case that wasn't enough, their guns were jet engine loud.

And this just keeps going and going- most tank engagements happened within 1000 meters, anything outside of 1500 was almost unheard of and most likely impossible to verify.

The Sherman wasn't really a bad tank- far from it, it was probably the most sophisticated tank of the war- but one need understand that between the guy who's story is, "I was in a tank for a year and change, we shot at stuff, some stuff shot back, nothing really happened" and the guy who's story is, "OH MY GOD EVERYTHING WAS EXPLODING AND MY ENTIRE CREW DIED AND WE KILLED AN ENTIRE SS PLATOON!" guess who's story is going to get repeated?