The whole tax system needs reviewing as well.
HMRC will pounce like vultures when those on the lower end of the wage scale get a pay rise. Not sure if it's still the case, but second jobs used to be taxed at a higher rate than the primary source of income. Side hustles - subject to tax on ridiculously low thresholds - Internet commerce being a huge target as it's boomed. In reality the effort of flogging off your old tat on Ebay or Vinted is often miniscule profit with maximum input, as customers expect individual hobby sellers to perform to the same alleged "standards" of Amazon and their ilk.
You sell a house - we'll have a chunk of that. You run a business - we'll impose rates that make your overheads unmanageable. You inherit, be it money or property - we'll have some of that. You want to drive a cab - we'll make you buy a license to operate that makes it unprofitable.
I'm not saying I'm in favour of no tax, just that the rules and thresholds make getting ahead harder at the bottom end. And the pursuit of this end of tax probably costs more than is generated.
Meanwhile, tax avoidance is legal and fully exploited by those with the most, so they can keep more quite legitimately, and any attempt to change that is met with threats by high earners and big employers to leave the country because they're single handedly paying for all the benefits and it's not fair, even though they are monopolising and ring fencing the employment market to garner the most profit for shareholders, enabled by the state to pay the lowest wages possible.
Big employers thrive on zero hour contracts and part time workers, because it cuts their wages bill and therefore their taxes. I appreciate part-time work is better for some, but again in retail and service industries and hospitality it leaves employees permanently insecure and still state dependent because of rising costs.
Round and round we go, which is why inequality is growing at an exponential rate.
Someone mentioned investment upthread, which of course can mean a few things, but in terms of the stock market, if you have 50.00 spare quid and buy shares in a big company, and that company goes bust, it's a pointless exercise - akin to playing the lottery or gambling. Unless you have multiple "spare" 50.00s, you're 50.00 down with no recourse. So "investment" when you're living hand to mouth is too high risk to try.
I could go on, but I hope you get the gist.