Mostly opinions and conjecture.
FACT NO.1. Fog, even snow, ice and very bad weather is current in northern countries.
There are THOUSANDS of planes every day landing on very bad weather conditions.
It's a question of not only the weather, but also the equipment available to navigate in those conditions. Smolensk military base did not have ILS navaids, so with visibility lower than minimum, most planes (and the IL76 before them) would divert rather than risk crashing.
The radar approach is not something most people would like to do.
If weather can be a cause of accident, then we would have all over the world
HUNDREDS OF THOUSANDS OF PLANE CRASHES EVERY SINGLE DAY.
There are plenty of plane crashes every day. They don't all make international news. Here in Ireland we had a fatal plane crash the day after Kasczynski's plane.
Also the Mirosławiec crash 2008 , I don't think made the news in Ireland.
FACT NO.2. Polish people are a nation of complainers. They like to be considered victims,
to cry and to complain. This is their national culture.
That's your opinion. It's a label a lot of nations get.
FACT NO.3. The russians lied until now about almost everything: they claimed that the
polish pilot could not speak russian, and other many lies.
The media are not Russian authorities nor are they a court, they rush to get headlines and accuracy is not first priority if there is no great risk of being sued.
FACT NO.4. All people present in Smolensk that day told that it was good nice weather.
Online weather website show that the temperature was between 7 and 18 degrees Celsius that day. Planes all over the world land without any problems on minus 20 degrees most of the winter in the northern countries, on total fog, and on an icy landing strip without any problems.
ATC Weather report I was referred to, said 1'C with 98% humidity. IL 76 diverted due to poor visibility, people on the ground and cameras show fog later on, and while possible to land in fog, it's usually cos the airport has good ILS equipment.
FACT NO.5. Polish pilot spoke perfect Russian and English. Captain Arkadiusz Protasyuk landed on the same airport three days earlier
Perhaps with much better weather.