Hello folks ...
Well who ever spoke of performance is absolutely right ...
The "classic" switch will do the job much more efficiently than any other implementation version.
I like the elegacy of the code above also but performance wise is nowhere near the simple "switch" statement solution.
I run a benchmark test (using the BenchmarkDotNet v0.13.7 package) for the above (renamed as AmIAfraid02) implementation.
The last one (AmIAfraid03) is the one using the "switch" statement.

See the summary for yourselves:

// * Summary *

BenchmarkDotNet v0.13.7, Windows 10 (10.0.19044.3086/21H2/November2021Update)
Intel Core i5-7500 CPU 3.40GHz (Kaby Lake), 1 CPU, 4 logical and 4 physical cores
.NET SDK 7.0.400
[Host] : .NET 6.0.21 (6.0.2123.36311), X64 RyuJIT AVX2
.NET 7.0 : .NET 7.0.10 (7.0.1023.36312), X64 RyuJIT AVX2

Job=.NET 7.0 Runtime=.NET 7.0

// * Hints *
Outliers
BenchmarkAmIAfraidMethod.AmIAfraid02: .NET 7.0 -> 4 outliers were removed (218.49 ns..220.67 ns)
// * Config Issues *

// * Warnings *
Configuration
Summary -> The exporter BenchmarkDotNet.Exporters.MarkdownExporter is already present in configuration. There may be unexpected results.
Summary -> The exporter BenchmarkDotNet.Exporters.HtmlExporter is already present in configuration. There may be unexpected results.
Summary -> The exporter BenchmarkDotNet.Exporters.Csv.CsvExporter is already present in configuration. There may be unexpected results.

// * Legends *
Mean : Arithmetic mean of all measurements
Error : Half of 99.9% confidence interval
StdDev : Standard deviation of all measurements
Ratio : Mean of the ratio distribution ([Current]/[Baseline])
RatioSD : Standard deviation of the ratio distribution ([Current]/[Baseline])
1 ns : 1 Nanosecond (0.000000001 sec)

// ***** BenchmarkRunner: End *****
Run time: 00:00:59 (59.8 sec), executed benchmarks: 3

Global total time: 00:01:05 (65.47 sec), executed benchmarks: 3
// * Artifacts cleanup *
Artifacts cleanup is finished

This still takes much more memory and CPU to process than a simple switch statement. It looks cool, but is not that clever.

No; it's easy to make that mistake on first glance, but a closer look reveals that the dictionary contains a series of lambda functions. Only the one selected by the key (day) is actually then executed.