This is true!
Psalm 145:9 The Lord is good to all, and his mercy is over all that He has made.
Salvation is God's loving mercy on the world.
Jeremiah 29:11 For I know the plans I have for you, declares the Lord, plans for welfare and not for evil, to give you a future and a hope.
The Lord's plan for welfare is to save the whole world. A future for all mankind. Jesus Christ as the hope for humanity.
Yet more scripture quoted out-of-context to make it appear to say something it does not say.
Jeremiah 29:1
(1) Now these are the words of the letter that Jeremiah the prophet sent from Jerusalem unto the residue of the elders which were carried away captives, and to the priests, and to the prophets, and to all the people whom Nebuchadnezzar had carried away captive from Jerusalem to Babylon;
Vs. 11 which you quoted was part of a letter sent by the prophet Jeremiah to the captives of Israel in Babylon.
Jeremiah 29:11-15
(11) For I know the thoughts that I think toward you, saith the LORD, thoughts of peace, and not of evil, to give you an expected end.
(12) Then shall ye call upon me and ye shall go and pray unto me, and I will hearken unto you.
(13) And ye shall seek me, and find me, when ye shall search for me with all your heart.
(14) And I will be found of you, saith the LORD: and I will turn away your captivity, and I will gather you from all the nations, and from all the places whither I have driven you, saith the LORD; and I will bring you again into the place whence I caused you to be carried away captive.
(15) Because ye have said, The LORD hath raised us up prophets in Babylon;
This passage does not say God will save all mankind God said "I will send upon them the sword, the famine, and the pestilence,...Because they have not hearkened to my words, saith the LORD."
Jeremiah 29:16-19
(16) Know that thus saith the LORD of the king that sitteth upon the throne of David, and of all the people that dwelleth in this city, and of your brethren that are not gone forth with you into captivity;
(17) Thus saith the LORD of hosts; Behold, I will send upon them the sword, the famine, and the pestilence, and will make them like vile figs, that cannot be eaten, they are so evil.
(18) And I will persecute them with the sword, with the famine, and with the pestilence, and will deliver them to be removed to all the kingdoms of the earth, to be a curse, and an astonishment, and an hissing, and a reproach, among all the nations whither I have driven them:
(19) Because they have not hearkened to my words, saith the LORD, which I sent unto them by my servants the prophets, rising up early and sending them; but ye would not hear, saith the LORD.