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much less prevalent now
Unless you're a rider in Costa Rica.
https://www.cyclingweekly.com/news/racing/two-costa-rican-cyclists-suspended-following-alleged-positive-doping-tests-449164Or Team Sky...
https://www.thetimes.co.uk/article/former-sky-doctor-richard-freeman-set-to-face-anti-doping-charges-dhb2wkzvkand this is not why I'm moving to Spain...
https://www.euroweeklynews.com/2020/01/30/epo-scandal-in-spains-andalusia-as-dialysis-clinic-epicentre-of-illegal-epo-trafficking/
I don't think riders improving from a high level is that uncommon, i.e. you could make the same argument for Thomas as an example.
We have every reason to be suspicious about unexpected improvements and teams whose attitude towards doping isn't as robust as others, but, as fans, there isn't anything more we can do to address this. Instead we have to trust that the UCI's anti-doping team are increasing testing on those riders who are showing unexpected improvements, or teams who show big improvements, i.e. like NTT this year.
Added: I realise this might be naive, but I genuinely think there has been a fundamental change in attitudes towards doping by a generation of riders and it is much less prevalent now than it was ten years ago.