You are right that this was a problem of the government's own making. It seems to be the normal way of government in the UK:
1. Media publicises an issue
2. Knee-jerk political reaction to increased media coverage
3. Rushed sticking-plaster legislation
4. Unintended consequence
5. Rinse and repeat
IR35 was a massively unwieldy sledgehammer to crack a nut. A nut nevertheless; when I was a contractor in the 90s most associates paid themselves a pittance of a salary and took all their income as dividend to avoid paying National Insurance contributions. When IR35 was announced, that nut was already about to shrink considerably because the national minimum wage came in in 1999; assuming enforcement was planned it would have been harder to pay yourself ~£60 a week while billing the client for 35 hours. Why successive governments have remained wedded to IR35 is a mystery to me. There must be simpler solution, for example a punitive tax on dividends which exceed a threshold based on the salary bill of the company?
But likewise there appears to be a nut now: e.g. MUC scams utilising the £4000 Employment Allowance. Imagine you are a contract services company and you win a contract to supply 1000 short-term staff for, let's say, a 'track and trace' system, if you set up 100 unrelated mini umbrella companies with a Filipino sole director, employing 10 staff each, claim the Employment Allowance for each company, then you have basically made a cool additional profit of £400K (minus expenses) on the contract at the expense of the taxpayer, and as a bonus your 'employees' have no comeback against you (or indeed anyone) if they don't get paid, etc. I suspect that this revenue loss to HMRC is the issue that is prompting the latest knee-jerk...