To discuss the measure of observance, it is important to understand the idea of what the [bar of the] accepted Halachic observance was.
a. Most of the Rabbinical decrees weren't established yet, so they kept practically Deoraysos only. We currently have thousands of detailed Halochos that we keep (are aware of) while back then they not only had the basic ones but hadn't them detailed.
b. The overall religious observance was total as the religions were the only explanation for natural phenomena, so just as we go to a doctor and take medicine when ill, they turned to religious authorities (usually Kohanim), brought sacrifices and observed cults. Remember, they had no alternative to religion, as we do, and they had not much choice but to observe. In other words, it was natural and automatic and required no special Emunah. In our reality, religion is superstitious and inefficient in explaining life processes so to be an observant Jew nowadays requires a lot of Emunah.
c. Social pressure: unlike our multicultural megacities and megastates, the life back then was extremely tribal - everyone had to rely on the community, and derailing from the common religious norms meant a boycott and expulsion, so again, not much choice. In our culture, not only that everyone has vital alternatives to being observant, but the constant criticism, objection, stricture of the religious lifestyle requires serious effort and Kiddush Hashem in following this path.
d. Sectorization and locality: the Jewish community was never uniform (as it is wishfully presented by some) - there was a very broad range of sects and communities from [what later became] Karaites to Perushim (but no seculars). As there was no single Halachic document, and as Rambam outlines the Torah transmission every Rabbi kept his own "scrolls of Halochos", Halachic observance was a very vague issue. FOr example, would you consider a 100% observant Karaite as a pious Jew? But what about an observant conservative or even a Reform Jew that strictly follows his Rabbi - would you call him pious?
e. Rabbis vs the rest - Halachah vs Chumrah: A lot of currently accepted Halachot that were codified by the Rishonim from the Gemmorah were just Chumrot that specific Rabbis held (most of the single opinions in the Gemmorah). So again, we are far more observant than they were.
f. Economical conditions: the observance was a subject to simple economical needs, local Rabbis allowed deviation from even Deoraytah, like R'Shimon allowing to sow on Shemittah, or Rabanan allowing Pikuach Nefesh on Shabbos. So the kept Halachah was de-facto one that "can be kept". Today, B"H, we have an unprecedented level of prosperity that allows keeping Halachic laws to the levels that nobody dreamt of. Just compare our Etrogs and Teffilins and whatnot to Chofetz Haim's or earlier generations'. We can afford different Meat and Diary fridges, have Torah scrolls checked by computers and many more.
g. Complexity of life: Talking of keeping Halochos, we nowadays have unprecedented levels of complexity on every Halachic issue. Take transportation on SHabbos - they only had two options - by foot or by an animal while we have anything from skates and bikes to cars and autonomous trains. So we must consider a far greater range of Halochos than they did.