The crisis in SS is going to be accelerated and exacerbated by today's economy in that the average worker is often a free agent. It's called the 1099 or the "gig" economy. The trend is steep in this direction wherein employers hire only temporary workers if demand increases and when it drops again that worker's gig is over. The worker is often off the books and neither contributes to the fund nor does the employer.
Uber is a prime example of the gig economy. Uber does not contribute to the fund as they consider every driver a free agent. Occupations like home care health, landscapers, roofers, nannies and tutors are all becoming more of the total work force becoming a significant share. It's estimated at 5-6% as of a couple years ago and I believe it is much higher today and growing. Eventually, if it is to survive, the general tax fund must be tapped.