It's bad that the tax treatment changes suddenly because businesses need stability, but the change itself is perfectly rational.
Profits = Revenue net Costs
Taxes are a cost. Taxes are defined as some rate t, tax = t * (Revenue net Deductible Expenses)
So Profits = Revenue - t * (Revenue - Deductible Expense) - Non-deductible Expense
Percent of t is small relative to the value of 100% applied to non-deductible expense. What this has done is to take salary, deployment infra, everything, from Deductible to Non-deductible expense, leaving 20% of what was there before. That is very large.
The issue is that the rules changed. Businesses that relied on the former rules are now faced with a (possibly insurmountable) challenge to accommodate the new rules.
Washington loves to fiddle with tax rules, and lobbyists spend a lot of time and money encouraging it, but nobody can anticipate the ripple effects. It all looks great on CBO spreadsheets and congressional press releases, but the real-world impacts can be devastating.
Previously, $1.000.000 spent on R&D in 2023 would result in a $1.000.000 deduction on your 2023 taxes. Under the new system the same spending would result in a $200.000 deduction in 2023, $200.000 in 2024, $200.000 in 2025, $200.000 in 2026, and $200.000 in 2027.
You still get the same deduction, but spread out over multiple years. However, it also means that you can now deduct $800.000 less in 2023 than expected, resulting in a far higher tax bill this year! If you are a startup you probably don't have that spare $800.000 just lying around doing nothing.