There is a HUGE difference between the GENERAL welfare, and the collective welfare of the individual. Items like universal health care, government provisions for health care, etc. etc. etc. are aimed at welfare of the individual in need of assistance, which is NOT the purview of the federal government. The GENERAL welfare is refers to the overall strength and stability of the infrastructure of government and society. IF that is healthy, then individual welfare benefits as a result. But if it is NOT healthy, perhaps due to things like unfair distribution of tax load, consistent and ongoing deficit spending by federal government, then it is those very factors that affect individual welfare, and greatly increase the need to assist those negatively affected. (Try reading up on the effects of using positive feedback controls on closed systems.)
There is a REASON for the existence of the 10th Amendment: to state unequivocally that the federal government's powers - and subsequent job/responsibilities - were specifically stated, and anything NOT stated is the job/responsibility of STATE government, or the people themselves. It was written so that brain dead, big government twits could not claim additional powers on a perceived-need basis, or base laws on stupid, ill-informed, ignorant-beyond-belief ideas such as suggesting the preamble actually grants powers.
(Yes, they failed at anticipating the sheer willful ignorance of those who want a mommy government to tuck them in bed at night. Had they anticipated how fucking STUPID people could become in pursuing their dream of making government responsible for everything, they undoubtedly would have worded it even more strongly.)
Also: the preamble states the overall purpose of creating the Constitution, but does NOT grant powers. It is the ARTICLES that actually grant powers to the federal government. The preamble says "This is WHY we are making this document" and the articles say "This is HOW our government is to function". Again, there is a huge difference.