You are making the leap that 90% of the virus is eliminated. It is highly possible that the 90% still happens, it just gets spread out.
Examine the logic of what you're saying -- Yes, if there were never vaccines and never improved treatments... then the effect might be just to spread it out.. and the people will die in 2021 and 2022, instead of everyone dying in 2020.
But if you develop vaccines and improved treatments -- And you "spread" those infections out so they would occur in 2021 or 2022, instead of right now -- Then you have vaccines and improved treatments, you save millions of lives!
It is also possible that some of that gets stopped if/when there is an effective and widely available vaccine. If one of the current phase 3 vaccines works and is widely available then flattening and elongating could lead to an overall lower number at the expense of unsustainable economic damage. However, what if these vaccines don't work and it takes another two years to get one that does?
Lots of "what ifs." But our scientists are very confident they will have at least a partially effective vaccine by late 2020, early 2021.
You also I'm not sure you can compare the peaks in Spain to the current peak in Florida. I can't find a chart for Spain but going from memory of the testing numbers for Spain, Florida is testing a higher percentage of the population per day now than Spain did at the peak. Florida is likely finding a higher percentage of actual cases now than Spain did at their peak.
At times., Spain was doing far more testing than Florida. At times maybe less. I wouldn't try to make it an exact comparison, down to the exact number of cases. It's very very very clear that Spain's case load was driven way way down.
BTW, why is Spain's drastic recent increase not a concern or a sign that the lockdowns didn't work as long term solution? Also, Sweden didn't lock down at all or implement mask requirements (at least as of a few weeks ago for masks) and their daily death number has continued to drop since the peak. Their daily cases also have dropped since a "spike" that lasted most of June.
There are so many factors at play that contribute to death numbers.... improved therapies will reduce death numbers, even as cases increase. Further, as you said above, I don't know whether cases are actually increasing in Spain now, or just testing is capturing a greater percentage of the cases. And we know, if more of the spread tilts younger, deaths may still somewhat decline. Finally, we know deaths are a lagging indicator -- the case increase in Spain is all over the last 1-2 weeks, so wouldn't expect to see it impacting death numbers yet.
Sweden -- something is very wrong with their data. They stopped reporting most of their data. And their strategy resulted in the absolute highest mortality in their region.
Now as to Spain's recent increase -- When did I say it wasn't a concern? A single lockdown, even done right, doesn't necessarily become a permanent long term solution. One of the reasons you keep testing (and contact tracing) is to quickly identify and respond to potential spikes. Depending on the type of spike, it may require different responses. May require a further lockdown in a more specific location, may require a re-evaluation of the operation of a specific industry, etc.