Ha ha ha lol! The first tanks didn't have guided air to surface missiles to worry about, did they? They went up against blokes with guns. So they were awesome weapons despite their crapness compared to today's tanks. Some potential 'first mech' which, let me remind you again, would be a ridiculous slow lumbering hulk with 0 advantages over a modern tank, would be wiped out instantly by already existing technology. Sorry to bust your teenage fantasies but mech wars ain't gonna happen, cool as it would be.
Each weapon be it old, current and future has it's positives and negatives but we still design them and produce them because we need them. The drawbacks of everything we have today is only limited by our current technology and process.
But as history has shown, we in time, always overcome everything as we develop new technology and new science. The first Mechs produced will be slow and lumbering, but as time goes by, they will change into fast, agile and deadly killing machines as we learn how to make them like that.
I hope you understand that all modern weapons today can be destroyed in a instant? But again, we still make these weapons.
If you still don't agree, think and look at old and current technology.
How big was the first computer? It needed a whole building to house it and how small is it now? How small will it get in the next 50 or 100 years?
Chip die sizes keep getting smaller and smaller, it won't be long till we all have chips inside our heads, the only reason we don't have such things is because our current technology and science hasn't invented how.
Compare the weight brothers plane to a modern day fighter jet like the Typhoon. The difference is night and day. Also, fighter jets can be shot down with air to air missles, but we still make them and use them.
Compare the old black and white TV's or Radios's to what we have today, we now have screens as thin as paper that Sony are playing around with. How long will it be till we all be replacing our big old monitors for these things?
The first mobile phone was nicknamed the "brick" because it was huge... in-fact I think one of the first ones had it's own case and how big are they now? Again, compare a old one to a new mobile phone today which can work as a phone, is internet ready, can play music or watch video.
You have no argument and in-fact you sound like generals from World War 1 and World War 2 who said Tanks have no use or value on the battlefield and that the horse was still the king of the battlefield, how much was they proven wrong in both wars.
They said the same about planes and the first planes that was used was for recon missions untill someone was smart enough that you could drop bombs from them, how quickly things processed from there.