It's not even up for debate. The plan helps businesses at the expense of individuals- there's no money to take from the lower income class, and there are just not enough super high income people to pay the bill even if we raised taxes on them (not to mention they would use their resources for tax avoidance). The upper 20% is the only bucket that can be tapped into
You are absolutely correct. The only way to raise the revenues is by broadening the tax base. The problem is that this bill isn't true reform, it's just tweaking and changing things, still allowing special interests to have an influence. Interestingly,
from what I've seen, the proposed bill gets rid of the Estate Tax, but doesn't get rid of the stepped-up basis, or impose a capital gains tax at death, which most estate tax repeal suggestions have as a reasonable offset (I really wonder which SIG managed to get the bill to include a repeal of the Estate Tax while keeping the step-up in basis).
The tax code is too long, and really needs to be entirely scrapped and rewritten in a simple way. There's no way out of imposing a VAT, and (I think) I'd much rather have it done when the Rs are in power, so that some limits and checks and balances are put in place along with it, rather than the Ds puting it in place.
Very importantly, true reform should eliminate (to the greatest extent possible) the huge tradeoffs that come with increased income (at least up to around $250,000 of income is reached). Having to worry about the next $1,000 in earnings costing more than just the tax on those $1,000, such as the loss of other benefits which were available without those $1,000, isn't something that does good for the individual or for the economy.
https://www.bloomberg.com/news/features/2017-11-09/how-to-break-out-of-our-long-national-tax-nightmare