The first eight episodes (two series) were brilliant. The digs were interesting, the conclusions neither sensationalized nor presented as fact with too little evidence. Alice Roberts guides the audience through it clearly and enjoyably.
But then, starting with the third series, it looks like the producers decided they didn't want to make anything so staid as perhaps the best archaeology series on English-speaking television ever. No, they wanted a talk show. Now tell me, what does that gifted young presenter need with a co-host? Is he there just to titillate the androphiles? Feh. I am one, and I couldn't get through the first episode.
When I skipped to the fourth series to see if they later got their heads back on straight, I discovered that they did change course, but not to their original format. Now they wanted to be a reality show, having the archaeologists at the digs record videos of the "moments of discovery" and send them in so that the "best" (in whose opinion? what are the criteria?) could be shown to the audience. Sure, there's a lab portion, but the videos looked so pointless and merely sensational that I couldn't bring myself to go any further.
I'm sure it's cheaper to send Professor Roberts to fewer locations, but if I wanted to watch a talk show or a reality show, I would have selected one of those to watch. I wanted to see a documentary. And after giving me episodes that I'd easily rate an 8 or a 9, they give me talk shows and reality shows, neither of which I watch because I consider them to be zeroes.
My advice is to watch the first eight episodes, and then give the third series onward a miss. Find yourself another actual documentary and watch that.