还有activity活动有什么替代词吗？

搜，用必应搜，用英文搜。 所有英语知识都应该用英文搜。你的例子里，搜 in recent years synonym.

没多少。in the last few years,

years/decades等，一个好句型是
Recent years have seen/witnessed that....或简单时态。

如果你还是用不了必应的话，下面是搜到的一些近义词：
over recent years
over the past few years
in the last few years
over the past several years
in recent times
over the years
in the recent years
for several years
for a number of years
of late
in the recent past
lately
recently
for a few years
for many years
these days
during the last years
over several years
in years gone by
newly

翻译不需要用那么高级的

用自已最熟悉的最保险，考试是为了过， 不是为了高级。

recent改成previous?

有没有想过替换掉“They lived happily ever after”或 "Long, long ago"呢？

真正的高手：用简单平实的语句表达高深的意涵。
好卖弄之人：用华丽浮夸的语句表达平淡的意涵。

这就是学校扯淡扯的，通用的说法不用，非要教学生整些花里胡哨的，还美其名曰高级表达

我写论文都用in recent years，大胆用，表达流利简单比表达怪异可好多了