They can't spend that sort of cash indefinitely. FFP rules will kick in and they will only be allowed to spend an amount relative to their income.They've had one transfer window and spent about 100m. If they continue to spend this sort of cash they are going to get better.
Also you need to buy the correct players. Everton have spent about £500M in 5 years (an average of £50M per window) and are in the bottom half of the league.
Spending £25M on Chris Wood isn't the type of signing that is going to allow you compete with top 6.