21'5 inch Imac TDM

Hi

I've bought a 21'5 inch iMac(2015) with hoping to connect my macbook pro to IMac via thunderbolt cable and show the display of my macbook on Imac

But as far as I seen iMacs doesn't support TDM(Target Display Mode) anymore.

Is that true?

If it is true, Do you know why apple disables TDM in newest IMacs and is there anyway to connect my macbook display to an iMac?

Thanks

Tolga