Full Stack developer career

Hello All,

I am a MEAN stack dev with 4 yoe getting only 5 LPA. I know it is way below the market standard but the manager says this is the market standard and nothing can be done. Is MEAN stack over saturated? Currently I see most of the openings are for Angular+Java and Angular+.net . Should I learn Java so that it will give scope for backend developer or learn React and go for React /MERN roles? I am well proficient in Nodejs. Need advice.