You have it backwards. The 21 year gap occurred precisely because of Vikings failure to find life. It took that long for NASA to get funding for another lander on Mars because the public lost interest in a lifeless planet that looked much like the moon, just with a thin atmosphere.

What do you think the odds are of another Titan probe after this one anytime in the near future if they did deliberately set out to find life and discovered Titan to be dead as the moon?

I'll see if I can dig up the articles I read decades ago related to the current slow, deliberately incremental policy steps toward identifying life on other planets. But it is not something I came up with on my own. This should not be viewed as a conspiracy but a determined policy to avoid a "failure" to find life and the subsequent funding cutoff that would likely occur. The reasoning for this should be intuitive and fairly obvious. It's quite surprising to me that you don't see it and say it is inconceivable that NASA would plan its programs this way when NASA has clearly been planning its programs this way.

As for the simple, low cost microscope (yeah with the necessary dyes), I think your argument goes back to the belief you have that alien life MUST be radically different from earth life. I don't really buy that. The same elements that make up life on earth exist everywhere in the universe. I believe it is likely they would share many of the characteristics of earth life especially at the single cell level. Sure I could be wrong but you too build a lot of assumptions into your arguments (e.g., the Micro-Titanians would shut down in a terrestrial spacecraft).

There are costs to everything. Costs for the equipment to analyze biosignitures. The cost of having the ability to just see if there are little living microbes is not prohibitive. That is my only real argument here.