I don't see major issues with cfd's and IG market, specially for beginners.
In the UK even IBKR offers CFD and the spread on instruments like SPY is the same of the ETF.
There is an overnight cost which might be high but acceptable for short term trading.
If you are trading options then it might be different, no commissions but higher spread, no Greeks... Binaries years ago...
I know two people who are profitable with cfd's and one with IG, trading mostly spy and qqq.
Ig has been around for around 30yrs.
The lawsuits I see when I Google them are like:
"The claim will allege that a UK-backed financial services firm, IG Markets, consistently marketed complex CFDs to inexperienced investors and facilitated those investors to trade in CFDs without applying adequate checks and balances."
To me, that translate into: the broker allowed idiots to lose all of their money with little due diligence to make sure they knew what they were doing.
Spread Betting is tax free and commission free. The spread on eurusd might be 1 or 2 pip extra, but not big deal if you are not scalper or a day trader, and if you are a beginner or a casual swing trader, a pip is acceptable.