I don't know for certain if there is any truth to these or not. And it's not up to me to figure it out. (That's what Police are for.)
I think that it's possible some allegations are true. However given how long the time from event until report about said event, (and how many seem to go right to the media rather than Police), I'll admit that I'm skeptical of them too.
What I mean when I say that, is that some of the reason these have been made public is because of money. Some people get greedy and make claims up against celebrities. (I think that's what happened to Michael Jackson... the families pushed the kids to make claims for a payout.) With how prolific some celebs are they aren't going to remember if they slept with some woman 15 years ago. So the accuser makes the claim to get a payout.
In other cases, like with Weinstein, they (the accuser) likely traded sexual favours for career advancement... But they have expected things to turn out even better (likely they compared what they got to others) and now they're just jealous/bitter that they didn't get as much as others did.
Plus with the dates of the issues being often times quite far back there's virtually no evidence to go off. So unless the person accusing made a terrible error (like they accused the person of indecent acts when they weren't even in the country at the time) it's hard to prove/disprove anything. And many celebs would seem to rather make a payout than have the person go public and attack with their reputation or career. (It's likely why Bill Cosby paid out, whether or not he actually did anything he didn't want them going public to destroy his image and make employment opportunities dry up.)
Though even if an accuser outright lied there is very rarely ever repercussions for those lying. False claims of rape/sexual harassment and the like are rarely ever punished. (Offhand there don't seem to be many publicly known cases,
the biggest one I know of only went forward because the woman claimed she was raped by 9 people in 4 occasions and got one man jailed for 7 years. That woman got a 10 year sentence for what she did.)