No - these companies generally don't have heavy debt.
1) IPO-ing companies represent a very very small chunk of the overall economy.
2) That 'there are IPO's' is a very good signal - it makes investors 'feel' bullish and confident.
3) These companies don't carry a lot of debt. If they were able to, they wouldn't be diluting by raising equity.
4) Uber, Lift, Pinterest, WeWork - they are all mostly viable businesses. Yes, their stock price may be too high in many cases, but they are mostly viable at some level.
5) Don't blame SoftBank. SoftBank is great! It's a ton of 'kind of dumb money' from places with way too much money (Saudis) and nowhere to put it. This means startups can expand far beyond where they normally would and they are handing surpluses to consumers like you and me!
Consider: how is it bad for you for companies to be giving you stuff below market value!? It's possibly bad for other investors, but we consumers win, so long as it doesn't happen broadly and cause a bubble.
All that money we send to Saudi for Oil is coming back in the form of 'cool offices below market value'.
Uber/Lyft have unit profitability problems at current price, but once the market settles down, they can increase prices a bit and it will be ok. (Again, massive stock price not withstanding)
WeWork will work out as long as there isn't a real-estate crash. They are basically leveraged hard on long-term contracts. We don't know the details of them, but if vacancies spike they could be in a world of cash-flow pain.
So yes, the hype is a little much, regular retail investors should probably we wary of holding the bag ...
But these things will only crash if there is a recession and most things look good right now.
FYI even 'bubble conditions' often need something to pop the bubble, like a sudden increase in interest rates, or 'the ground falling out' like in 2007. Right now, there are some signs of froth, and hints of maybe a recession (i.e. at the top of the cycle) but nothing really to say it's going to pop.
Canada could have a major real estate correction, but nobody would care.
China could have a flop, but they can fudge the numbers so well it'll probably be covered up and papered over as a long term slow down. In fact, I think that's what's happening: China has many big sectors which would be in recession, but the numbers are fudged to look like 5% growth.