Since when has it been the case that you are informed that you are going to be interdicted????
Since ages back.
You get a message on the Comms panel, something like, "The rumours were true! Coming here with a cargo like that, you are asking for it, Commander. Now you're MINE!"... I don't have Music enabled, but it probably goes Dun-Dun-DUUUUUUUUUUUUUHNNNNN as well!
Thing is, you might get a couple of seconds before they interdict you, especially if they're close and you're busy with something else or haven't noticed this one warning.
I mostly get caught out after a long trip, or if I'm coming to the end of my game session and am tired... which is no consolation for losing many millions. I also get caught out because if you don't submit quick enough, that counts as a struggle and even if you then submit, you end up spinning out and taking damage, so even if you hit Boost the instant it's available (which you can while still in the spin) you're already under fire from either the interdicting NPC or more likely his escorts who have Wingman NavLock and drop in under full control, weapons out and in position to head you off.
Happens like this more at the upper end of the Combat ranks, with NPCs in bigger, tougher, engineered ships, but can still be a problem for lower ranks, too.
I am sure they never used to give a warning
They did, but it was one line in the Comms. I expect you're only noticing it now because the flag is much larger, with an NPC's avatar displaying. Before it was easy to miss, especially as you're most likely focussing on not crashing into the whacking great star in front of you... and that's where the 'mistakes' happen that end up getting you killed. Perfectly human mistakes, of course, but still one of the reasons why I prefer to have some measure of additional defensive options.
Spent 20 mins going to alien ruins.... Same as all other alien ruins.
Oh no, we are SOOO sorry to hear about your troubles and dissatisfaction with the game.
Is there anything we can do to make it up to you? Perhaps direct you to Frontier's contact page, wherein you may request a refund or direct your complaints to them along with a list of exactly what features you feel they should implement in order to provide the experience you require of them, or would you rather we suggest you go play Star Citizen?