In the book it's mentioned that for all the technology the Martians never seem to have invented something as simple as the wheel, what are the Martians so fascinated by when we see them outside their tripods? A bicycle wheel.
A lot of people complain about the ending — where the Martians die suddenly of diseases resulting from Earth's bacteria that they are no longer immune to — as being a Deus ex Machina that comes out of nowhere to solve the plot. Read the first chapter again. Literally the first paragraph of the book — and every adaptation which draws on it — compares the way the Martians look at humanity to the way humans look at bacteria; dispassionately, as something small, insignificant, easily dismissed or forgotten about. And yet any expert will tell you that in the right conditions bacteria can be devastating. The ending was hinted at right from the beginning... and if you forgot about it, you made the exact same mistake the Martians made.
One frequent problem for European colonists were the diseases in the colonies, diseases they had little defense against without medicines. Back in the day the book was written, this was well known. Africa itself was informally known as "the White Man's grave" because of all the tropical diseases that only the locals had evolved any significant defenses against, Malaria alone being pretty much the deadliest disease in human history. It's not a coincidence that the Scramble for Africa (which was ongoing when the book was written) only happened AFTER Quinine became available.
The reverse was also true: colonists bringing diseases the native population had no resistances to, killing them en masse (smallpox, to name but one). Disease and its spread are intertwined with colonialism, so it's completely natural that this allegorical critique of colonialism features disease as its most central plot point.
Wells frequently uses the railway as a symbol of civilization, how easily it can be overturned, and how it can be repaired. The human complacency in the face of the Martian threat is represented by trains ferrying people to and from the local railway station despite the arrival of extraterrestrial beings. The attack on Woking is symbolised and discussed in terms of the destruction of the station. The great panic is represented by people crowding London's railways stations desperately trying to board a train to safety, and it's mentioned that some drivers are even ploughing their engines through the crowds in their desperation to flee. And at the very end, when the invasion is defeated and life is rebuilding, the narrator returns home by train.
Why did the Martians make no attempt to chase down the refugee boats after the destruction of the Thunder Child even when it was clear they could have taken her out quickly and without losses had they used the heat rays immediately? Either the third tripod had been sunk by the Thunder Child... Or the pilot had ran the hell away from the Channel Fleet reinforcements, them being three warships that were likely bigger than the Thunder Child (the Thunder Child being a small torpedo ram, if an anomalous one, left behind as rearguard, and the other ships being most likely battleships).
The Thunder Child being a torpedo ram also explains why she was the only ship there: she was expendable, and intended to hold the line and distract the Tripods just long enough for the actual battleships to come into range and open fire... Except the Martian ships were thin-hulled and unprotected enough the expendable ship was enough to take on three of them.
The Martians' inadequacy when facing ships could be explained by the fact that Mars has been drying up for quite some time. It stands to reason that naval combat hasn't been viable there for a while. This could also be viewed as an extension of the anticolonial metaphor. One obstacle many colonial invasions often face is being horribly ill-equipped for the environments they're invading, giving the locals, who are used to fighting on their local lands, a home-field advantage. It's often not enough to thwart the invasion entirely, but it's a massive roadblock a lot of the time.
It's often noted that Torpedo Rams were generally proven to be ineffective in actual combat, however despite being far more advanced pieces of technology and weaponry, the tripods being well, tripods makes them more prone to being knocked off balance if a leg is damaged, making the completely obsolete for Earth warfare Thunder Child an ironically viable weapon.
The Martian tripods were the scariest, deadliest, most effective weapons that Wells could think of in 1898. In just twenty years, humanity would have the weapons technology to reach parity with these weapons, including some of the very same weapons (chlorine gas being similar to the black smoke). And then, about a century later, humanity has invented weapons far more destructive than anything the Martians ever had in the original novel. Man's capacity to kill itself far outstripped what even science fiction writers could concoct.
