Hard disagree, as again, the republican party exists. It was a third party.
Practically no one votes strategically. The vast majority of voters vote the same as their parents and/or peers. The extreme minority of voters that care about issues vote for whatever party of the two that suits them best at the time.
But bigger than all these groups are the eligible voters that think nothing will change because people like you tell them they only have two options, so they don't vote.
Because neither option is good. There is Nazi, and there is the group that appoints nazis. Both exist solely for their own power and wealth. Neither help people until the riots get too violent. So why vote. Why care?
So either we introduce a third party or more, and maybe give some hope, or we let the uniparty continue to win and we all have to survive a balkanized US when it collapses.