I think Greg just missed a bit when he answered. So his answer is good. I'll just add a few points. back in time - normal. Yours is not wrong science and technology were (were) The internet and technology were not common. (The) People would usually entertain (entertain) themselves or get information ("through" unnecessary) watching news on ("the" unnecessary) television. (televisions--> television) ... people have become indifferent to the real life. ("in" is nmot wrong, but I suspect you mean "indifferent to" ) "at their" --> "at their" "would" is not the best choice here. This suggests that watching TV means they looked at their phones. "couldn’t " the same? --> "they don't realise how beautiful " They spend most of their time ("on" unnecessary) looking at their phones instead of people and things around them so that they don't realise how beautiful the world is and how short their life is and they should not waste their time on it. As people is plural, probably should use "their lives are" Not entirely clear what "it" is. Technology? or as Greg assumed, is "their time on it" meant to mean their lives?

Note: I've capitalised the words where I've made changes to make it easier for you to spot the changes. I sometimes wish I could go back to the past. This is fine. More colloquial to say "I sometimes wish I could go back in time". About ten years ago, science and technology WERE not well developed. AT THAT TIME, internet and technology were not common. People would usually ENTERTAIN themselves or get information through watching news on TELEVISION. Interacting with each other makes me feel warmer and MORE real. Nowadays, with well developed science and technology, people have become indifferent in REAL life, SPENDING most of their time LOOKING at their phones instead of people and things around them. THEY DON'T realise how beautiful the world is, AND how short their life is and THAT they should not BE WASTING their time DURING it.