Is it still worth mining bitcoin in 2018 ?

Mining is a process which requires a heavy investment. I don't think that mining any cryptocurrency with the help of a basic computer is possible these days. You will need high-performance hardware(system) that is capable of evaluating multiple(quintillion) hashes per second. High-performance systems are not that cheap, firstly they are costly and require a considerable amount of space to set up. So now the decision depends on you whether you are ready to invest heavily or not.