It's basically a binary choice. You either have a home defence force - FJ DCA, AEW, SH, shore ASM batteries, MPA, SSK, MCM, OPV and a rump army. Or you provide useable effect at a strategic level and in doing so, do some of the heavy lifting for your NATO allies. The "in-between" doesn't add that much for all the extra cost.
Lots of NATO countries can supply FJ, DD/FF and infantry - of varying quality, but they're not exactly scarce, even if their RoE can be constraining.
No-one else - at present - can provide the top-end naval assets in Europe, apart from the US and France (when CdG is available). Which is one reason why they're very keen for some assistance and why they've been very generous in supporting regeneration of carrier strike.